Yeah, slow lands aren't all that slow and checks come in untapped in the vast majority of situations. In my greediest mana base that runs a total of 6 basics in a 3-color deck there are still 19, 17, and 16 "turn 1 hits" respectively for the three checks to come in untapped turn 2.

FWIW I run 2 checks, 2 slow lands, and 3 Lorwyn/Shadowmoor filters in that particular 3-color deck. Filters are great but they are not risk free. You have to be pretty confident that you will be able to pay into them.

120.4a defines excess damage in detail. The relevant part of rule 120.4a is that "the excess damage is the amount of damage in excess of what would be lethal damage, taking into account damage already marked on the creature and damage from other sources that would be dealt at the same time." The 1/1 already has 3 damage marked on it, which is above the threshold for lethal damage to it. So the entire 3 points of damage from the second Lightning Bolt is excess damage. A Blindblast after the first Lightning Bolt would also trigger Aegar.

120.4a First, if an effect that’s causing damage to be dealt states that excess damage that would be dealt to a permanent is dealt to another permanent or player instead, the damage event is modified accordingly. If the first permanent is a creature, the excess damage is the amount of damage in excess of what would be lethal damage, taking into account damage already marked on the creature and damage from other sources that would be dealt at the same time. (See rule 120.6.) Any amount of damage greater than 1 is excess damage if the source dealing that damage to a creature has deathtouch. (See rule 702.2.) If the first permanent is a planeswalker, the excess damage is the amount of damage in excess of that planeswalker’s loyalty, taking into account damage from other sources that would be dealt at the same time. If the first permanent is both a creature and a planeswalker, the excess damage is the greater of those two amounts.

I took a look at 5 of the decks and to me they all have the exact same problems that pre-cons have, so it is unsurprising that your more experienced opponent is winning with pre-cons. Your mana curves are outrageously high with too many lands and not enough ramp.

Comparing your Colfenor, the Last Yew deck to my Ghave, Guru of Spores deck that has been purposely powered down to not stomp pre-cons and my Hapatra, Vizier of Poisons deck since you have access to at least all the cards I run in those decks. You have an average CMC of 3.69 compared to 3.64 (Ghave) and 3.11 (Hapatra). This makes it so that you need more mana to do anything.

You run 37 lands and 5 ramp (I am not counting anything over 4 mana, as that is what you are ramping into, not when you want to ramp) as compared to 33/19 (Ghave) and 33/11 (Hapatra). For my own counts I didn't count anything over 3 mana or the altars. This makes it so that you are waiting longer to get your mana.

Abdel Adrian, Gorion's Ward has a trigger with a duration like Banishing Light and Banisher Priest, not an ETB and a LTB like Oblivion Ring and Fiend Hunter. The effect ends and the permanents are returned as soon as Abdel Adrian, Gorion's Ward leaves the battlefield. This is not a trigger and doesn't use the stack. The exiled permanents will be returned before Abdel Adrian, Gorion's Ward re-enters the battlefield and can be targeted with the new ETB to be exiled again if you wish.

(Also, for reference the site contains a rules Q&A where you can ask rules questions that is frequented by many extremely knowledgeable users. Some of which may not necessarily see a post in a format forum.)

That works, you just hold priority and keep activating it.

Kinda depends what level the event was being judged at. At Competitive and Pro REL you might be, but are not necessarily looking at "Tournament Error — Communication Policy Violation". I say that you might not have made an infraction because the IPG requires that the judge determines that your opponent took an action, or chose not to act based on the communication policy violation. Worst case scenario for you is a Warning and a backup to when the action was taken/not taken. You opponent because he didn't fix his life once you informed him of the mistake definitely committed "Game Play Error — Failure to Maintain Game State" (warning) when he didn't fix his life total and based on his reaction in general I would say "Unsporting Conduct — Cheating" which is a DQ.

At Regular REL (assuming that the event was being judged here unless your LGS judges at Comp for some reason) the fixes are a bit more relaxed and it may be worth just quoting the entirety of the section of "Judging at Regular" that would be relevant. Judging at Regular is actually worth a read if you plan to attend tournaments judged at Regular often as it is only 2 pages long and will help you understand what the judges are doing.

"A player makes an in-game error not mentioned above. This will cover the bulk of player errors, and usually the least disruptive option is to leave the game as it is after fixing anything that is currently illegal (e.g. an Aura enchanting an illegal permanent). If the error involved a player forgetting to draw or discard cards, have them perform the appropriate action now. Otherwise, if the error was caught quickly and backing up is relatively easy, you may undo all the actions back to the point that the illegal action happened. This can include returning random cards from the hand to the library to undo card draws (though don't shuffle the library if you do this), untapping permanents and undoing combat. This can be very disruptive where lots of decisions have been made or hidden information has been revealed since the illegal action, so don't go crazy with this!"

Your opponent would choose one of their goaded creatures to attack with. You have to fulfil as many requirements as possible without breaking any restrictions when declaring attackers or blockers. Your opponent still gets to declare their attackers. They will only be able to fulfil the requirement of one goad without breaking the restriction on Mirri.

508.3a An ability that reads “Whenever [a creature] attacks, . . .” triggers if that creature is declared as an attacker. Similarly, “Whenever [a creature] attacks [a player or planeswalker], . . .” triggers if that creature is declared as an attacker attacking that player or planeswalker. Such abilities won’t trigger if a creature is put onto the battlefield attacking.

There are many cases of cards that are one color giving tokens of another mono color. The easiest one to think of is any non-white card with embalm. I would like sticking with 4/4 red Dragons just to minimize the number and type of tokens in the game. Not that it matters since there are hundreds if not thousands of different token types already.

I am partial to replacement effects for messing with tokens, I'm also not really a fan of the aesthetics of an ability referencing itself. Kodama has a cool design, and I'm sure that they went through a lot of iterations of the ability to make it as elegant as they can, which is why I took inspiration from him. I just don't like it for completely arbitrary reasons.

Overall I like the design. It could be useful in certain decks, but isn't generic enough as to become ubiquitous.

A formatting tip:

Looking at what "would" happen is something replacement effects do. Looking at what did happen is what triggered abilities do. You need to bring the templating into accordance with one or the other. Since this type of effect is usually a replacement effect (denoted by "If...would...instead"), I would change it to a replacement effect using Chatterfang, Squirrel General as inspiration. "If one or more tokens would be created under your control, those tokens plus a 4/4 green Dragon creature tokens are created instead." Alternatively you could make it a triggered ability, but you would have to exclude tokens made by itself. To do this I would take inspiration from Kodama of the East Tree. "Whenever one or more tokens are created under your control, if they weren't created with this ability, you may create a 4/4 green Dragon creature token."

It is pretty impossible for something to get "stuck on the stack". When a spell/ability goes to resolve if it is targeted and has no valid targets it is countered by the rules of the game (fizzles). If it is an untargeted spell/ability or still has legal targets it will do as much as it can and then leave the stack. Sometimes "as much as it can" will be nothing.

Without a specific example of what you are thinking would get something stuck, it is really difficult to address how it would be handled.

Myriad is an attack trigger. Attack triggers only trigger on the declare attackers step as a result of creature being declared as an attacker as a turn-based action. You will not get Myriad copies for a creature put in tapped and attacking with Ninjutsu.

702.116a Myriad is a triggered ability that may also create a delayed triggered ability. “Myriad” means “Whenever this creature attacks, for each opponent other than defending player, you may create a token that’s a copy of this creature that’s tapped and attacking that player or a planeswalker they control. If one or more tokens are created this way, exile the tokens at end of combat.”

508.3a An ability that reads “Whenever [a creature] attacks, . . .” triggers if that creature is declared as an attacker. Similarly, “Whenever [a creature] attacks [a player or planeswalker], . . .” triggers if that creature is declared as an attacker attacking that player or planeswalker. Such abilities won’t trigger if a creature is put onto the battlefield attacking.