If you do it now it is not your fault. I do not endorse divorce, but being essentially cuckhold is not a good option either.
I guess worst come to worst if she wants to leave the relationship dysfunctional, you could always get your own lover, and isolate your life from hers.
The question is what do you want your kids to see as normal?
I am actually considering the lover thing now. It sickens me to think about it. But there it is. I dont know. Most of you guys are dead on about this. I have always known that. Its not that I dont think that the best option probably is divorce, I just am trying to find anything else that will prevent that.