Good luck HOneypig - you will get through it. The silver lining of your approach is that you can know in your gut that you did everything possible to give him every potential chance and you can have peace and no regrets about that. That means something. So you aren't in exactly the same place as you were 18 months ago, even if it feels that way right now.
(I say this based on my own experience as I've just started internalizing this myself since I felt like I should have kicked my A out 18 months ago when I discovered the cheating, but it took me until this summer to do so, and he still ended up with his mistress. But I have no regrets that I gave the marriage a chance and him the chance to declare himself, and he declared himself to be a lying A, so that was that)
SR is here to catch you!