This will probably get deleted. But, take it as general observation about this kind of thing in general. He has already played his cards and it really doesn't matter much what any of us says to HIM now.
OK, first, why are you sharing this with us - and promising updates - if CDing is behind you and you're saving your marriage? Is this part of some ebook you're working on?
Second, I'd like to see this "nice" four page letter. Nice? I HATE the "letter" gambit. Gutless, thoughtless, and, clueless. Say it don't play it. Think how long someone will be going down that page to hell. And, get a clue what she expects - NOT a letter! How about some conversation... You know, the one you've been skipping since she met you?
I'd divorce you. There would be no way around it. Why stay with a bonehead?
This is no crossroad. The is a sign in the road.
And, this is no good deed, it's just a deed.
Boo!
What else is on?