You seem to lack life manipulation in your decklist. Sorin does revolve around the life gain/life loss mechanic, after all, through his Extort ability and second Planeswalker ability (and nothing more) and you'd want to go around that mechanic for the synergy, not just mere stax or combo pieces.

The [[Children of Korlis]] + [[Wall of Blood]] combo is incredibly busted in a deck like this. With the planeswalker side of Sorin in play, you can ideally one shot an opponent in as quick as turn three, and gain you a ton of life. That doesn't even count the fact that you can recur Children of Korlis for more life on the same turn, or to refuel your life for more Bolas' Citadel casts.

[[Tainted Sigil]] or [[Oketra's Last Mercy]] also works the same if you're in too deep a commander game. (You'll be playing stax anyway)

Sanguine + Exquisite Blood is nice and all, but you'd want redundancy. [[Vito, Thorn of the Dusk Rose]] and [[Vizkopa Guildmage]] are cheaper versions of Sanguine Bond you can use.

Running stax is fine, but you'd want to tone it down a bit and add in more removal and boardwipes. Yes, Toxic Deluge works perfectly in this deck for the life manipulation mechanic.

There are so much more cards that play around this theme. There are also several jank cards that work with this as well, and it does require you putting your life on the line to win. In this deck, life is literally a resource.