With the lifegain aspect, something you could try is Wall of Reverence and Serra Avatar which doubles your life total every turn, while giving you an insane beater. Individually, they both work with what your deck wants to do and together they combo well. Here, I would so potentially Azor, the Lawbringer and potentially Propaganda to switch out if you want to try these cards. In general, Azor, the Lawbringer can be good, but I don't see a way to blink him. You also have PLENTY of draw spells without the needed obstacle of attacking. If you need something to attack with, a huge beater might be a better choice.

I want to second the suggestion of Beacon of Immortality as it can be a wincon with Sanguine Bond. I use this in my own Oloro deck and an instant speed wincon comes in handy quite often. I forsee you potentially taking out a land here. Even with 37 lands, you have five rocks. You shouldn't have any problems getting your lands with the amount of draw you play.

With the amount of enchantments you have in the deck, I feel that you should replace Norn's Annex with Sphere of Safety. Other lifegain decks can pay that tax, and big creature decks are willing to pay 2 or 4 life with their 20/20 creatures. Sphere of Safety makes people tap even more mana to attack you which could be the difference in whether they actually swing or not.

These are just my initial suggestions, and disclaimer, I did not look through all of your past updates to see what you have tried. These are just my suggestions based on what I see with the deck as of now.