Some observations:
One thing that strikes me is the focus on what you did with your AP vs. what you did/will do with your husband. You are VERY clear that some of the things you did with the OM you view as disgusting, immoral, and transgressive, and that you don't want to do them again. And that is entirely your right. But this leads directly to the question "If these activities were so vile, WHY did you do them?" Was there force involved? Blackmail? You must be able to answer this question - not necessarily here, but definitely to yourself and your BH. I have the suspicion this is the root of his fixation - he already knows the what, but he needs to know the *why*.
Second, the monetary situation. You say you have 2 incomes, and you also state that he controls and/or is hiding all of the money. If so, how does he have access to your income? You seem to be uneasy about what he's doing with the money, but you don't seem to be taking positive steps, such as depositing your money in a different account.
Third, what is your source for what he can and cannot do vis a vis divorce and custody? Has a lawyer told you that he will get full custody? A friend? Has your BH claimed/threatened this? Or are you just assuming it?
From your description of the situation and the way you write about it, I would hazard a guess that your relationship with the OM was basically a submissive one, both sexually and otherwise. And your relationship with your BH also tends to be submissive, but you don't want it to be. You believe that if you just do what he asks, he should be satisfied. And since he's obviously not satisfied, he's not holding up his end of the relationship. But you value the relationship and don't want it to end (at least not on his terms) and feel trapped.
You are trapped, but it is one of your making, and it's a trap of false assumptions. First, you CANNOT "fix" the marriage, at least in the sense you imply. There is no making up for what you did - it's a hole that cannot be refilled, a debt that can never be repaid. So stop focusing on counting the transactions and wondering when the payments will be over. Instead, focus on:
a) understanding why you did what you did, and working on those parts of you that need strengthening
b) understanding the stresses in your marriage, both post AND pre DDay, and work on your end of those, and
c) accept that he can choose to walk away, and so can you. The choices may all be bad, but they are still choices.
This last one is probably the hardest, because the ability to choose requires you be responsible for the consequences. It sounds like you've been letting others choose for you (which is still a choice, btw). And you've seen where that's gotten you.
