In fact the way I had originally worded it, I took on too much responsibility for abuse.
In my opinion, you still are. I know you are hurting, but you are SO full of "I'm sorry's" right now, that you are coming across as taking the blame for your wife's decision to have an affair. Until you stop doing that, I don't think she'll respond to you.
You need to better find that line between accepting your 50% responsibility for the condidtions that led up to her decision, but NOT take ANY responsibility for the decision itself.
It's a fine line, but it's a critical one, and if you miss the mark, you come across as WEAK. I think you're struggling at it.