I guess the best thing I can do since I am not around enough to follow any threads is to tell you that all can be well after sitches like yours. I'll try to play cheerleader.
If you read my entire story (you can find the links around here somewhere on my threads) you will see that mine was probably a lot like yours in some ways, maybe a bit different in others, but on the whole, it was a crap situation and it was REALLY hard to get through.
I would say that through this site, the books, and support of the great people I met here, my marriage is stronger than ever. I am one of those people who actually say that this process, the cheating (her not me), the lies, the betrayal, the pain, all of it was worth it. I really mean that.
I would NEVER suggest that anyone use this kind of thing as some kind of twisted sage for their relationship woes but if you're give lemons, well, you know what they say to do with them...
Just know that IF you learn to extract from this experience, this terrible, heart breaking experience, the copious amounts of GOOD in terms of self awareness, growth and learning to be a more compassionate human being, you can come out ahead of the game.
I know I never had to get to the point of completely giving up on my marriage, as some have to do before they get to the point where things start to turn for the better, but I was prepared to do that in the name of learning what it truly meant to be caring for myself and worrying about my own well being so that I was healthy and happy enough to provide for my kids and what was left of my family.
If nothing else, you should take away THAT lesson from all this. My wife still has that to learn. She still hasn't figured out (except for that little affair) that she needs to put herself first sometimes and take/get what she needs so she can give us what we need from her. Hell, I still defer too much and my passive/aggressive nature still lingers, but the key difference is that I now notice EVERY time I start to think that way and make a conscious decision to continue...or not.
You CAN do this. Whatever your sitch seems to be demanding of you, whatever that annoying vet on the boards keeps asking you do, you CAN do it.
You just have to realize that to get to a different marriage, one that is whole and vibrant, you have to become a different person, a whole, vibrant person. You have to be that guiding force and not let this sitch, or your wayward spouse be that anymore.
Affect change in your life and it will carry over to your marriage.