I think his letter is sincere, and I think he still loves you.
I also think he's weak right now (maybe always has been?) and his letter is full of self-excuses for his own poor choices, and that would be a major concern of mine going forward, if I were you.
It's also a bit alarming (and telling) that in 1,800 words, nowhere does he say that he has ENDED IT with OW, once and for all, or what he's willing to do in that regard (transparency) to earn back your trust. As I said in my previous post, I don't think he even has.
THAT is where it has to start, in my opinion. But before even THAT, you need to determine if you want him back, and unfortunately we can't answer that for you. To me, he sounds like a good guy, and he obviously loves you. I just think he's a WEAK guy, and at this age, tigers rarely change their stripes too much.
I can't remember: was there any prior infidelity with him, either with you or a previous relationship of his?
