Ask him straight out what he's looking for. Offer to have an account for yourself only and give him what he contributed. Let him be responsible for his money and you yours. I know it sucks to do this, but he is, after all pushing the ticket.
He's trying to find a way to get to you, and it seems as if he may have found one. You've done nothing wrong, throw it back in his court and let it end there.
He's trying to "get you" on something, after all he is taking your recovery as a personal attack on him, which it's not, so it only stands to reason he is looking for something on you, to show you that you're not perfect either (which I think you already know, none of us are perfect). Don't let this throw you LNF, this is very typical of the alcoholic mind set, at least in my experience.