Put Yawgmoth's Will back in and cut solmen. Yawgmoths will is too powerful to ignore and will be useful mid-late game while solemn is only useful early-mid.

Mastermind's Acquisition Is a great card to combo with Xiahou Dun, the One-Eyed. You can make a 15 card board and put some cards in to help against certain decks that gives chainer some issues (blue white control--Nevi's Disc, Hero's Downfall and the like, Sword of Sinew and Steel, etc.) it allows you to run 15 extra cards without having them eat up space in your deck.

Attrition and Overseer of the Damned is a fun combo. I have gotten tons of use out of attrition.

The Rings + Basalt combo is nice, but I ended up dropping it out of mine. It is nice if you play Torment of Hailfire and Exsanguinate but I went more control than combo after a while.

Thought-Knot Seer is great for some recurring hand hate

Tevesh Szat, Doom of Fools has been an all-star in my deck, you could also add Karn Liberated and Ugin, the Ineffable for more pointed permanent destruction

Flesh-Eater Imp is also a fun sac outlet and an alternative win con.

Volrath's Stronghold is good for saving some of your cards from graveyard removal and I have been debating Phyrexian Reclamation and or Tortured Existence. Fortunately I have not seen too many EDH decks with a lot of dedicated grave hate.

Disciple of Bolas is also an all star card, he keeps chainer going like you wouldn't believe