"When I originally wrote this, he had a look of confusion on his face. I believe I read a lot into it."

I question this thought somewhat.

I do so because of this...

"When I told him that maybe it was me that needed to change, I think now that it gave him an out and a reason for his affair."

You told him that you needed to change. and he felt you were being honest.. right? Why does that give him the right to have an affair?

"I want him to be happy regardless of whether or not that happiness includes me."

OK.. so mimic this thought.

Explain how you might do that.

Or

What does that statement mean to you?

Relax
Eat
Think
Act normal
React.. Smartly.
Do something different.
Emulate.
Do Work.

Lets get "RETARDED" in here.