He blames me for divorce! Why is he so angry?

[woundedfool]

I made it very clear to him that I will not tolerate infidelity in our M.

While you do mention a realization other M have survived A's... You do seem fairly rigid it is a deal killer for you (I am not judging that, just want to clarify something):

If I did find evidence it would relieve the burden of failure on my part.

In a sense, I detect you hope to find an A... that way, you have an "out". So, I am going to lead to something a bit tougher, that will involve some deep reflection on your part:

I've lived that part in my first and second marriage and have watched my mom go through it. It's no picnic and I will not put my kids through that again.

So you had it in your first M... the second M.... and now potentially the 3rd M?

Different husbands, but the same W.... Why do you think this pattern is repeating?