Hey there guy,
First of all, I made my significant other read your posts and it has actually in the span of a day, helped us. So thank you.
Second, you're beating up on yourself. You need to stop this behavior, for your health. I have experience in mental health, are you seeing a therapist? You sound beat/depressed, I mean who else wouldn't be depressed with what you're facing. This is a loss. There are 5 stages to loss/grief and you are full on in the Bargaining stage. The stages don't go in a particular order, but you sound trademark. Secretly, we may make a deal with God or our higher power in an attempt to postpone the inevitable. This is a weaker line of defense to protect us from the painful reality...sounds like you.
It sounds like you made some mistakes and you tried to fix them up. You think you were too late, well it took you some time to get there, meanwhile your W went ahead and had an affair. I mean comeon, she needs to grow up!
Third, stop beating up on yourself, again.
Fourth, stop making excuses for her.
Fifth, worry about your kids as top priority and then yourself and then her, as you can see, she is worried about herself and the OM before her own kids. I know you feel guilty for not being there for her for 5 years, but you've unleashed your power. I mean, I'm worried that she's walking all over you vulnerability...not healthy at all.
Sixth, keep writing us. Good work!