I'd recommend
Phyrexian Crusader, especially in our metagame (TONS of white removal). Additionally, I'd consider some discard spells (
duress, or if you wanna get fancy,
thoughtseize).
Also, replace corpse curr or other higher CC with plauge stinger -- the evasion (flying) and low casting cost make it significantly better.
The best card ever for a deck like this is
Inkmoth Nexus, but that's a bit pricey. I'd also consider looking into some equipment -- affordable options include
Bonesplitter, with less affordable (but more powerful) options like
Sword of Light and Shadow,
Sword of Feast and Famine, basalisk collar, and others.
Finally, keep this in mind -- this is a control deck right now, but you could possibly go for more of a speed deck. Infect can kill very very quickly, especially with unbloackables, but it seems like a good gameplan to play infect creatures with evasion, counter those things that could
disrupt your plan, and just attack for the win.