Bigger things I want-- like saying to me that he doesn't give a rat's @ss about AP anymore-- that he won't do. He is pretty explicit that he isn't going to say anything just because he knows I want to hear it, unless it is true, and that we can't fast-forward to that place. He has to get there authentically.
I have been reading along with you these past few weeks but not posting much. I'm not sure if you want advice, or. not, so please forgive me and ignore if I overstep. But this, above, what your husband is saying to you - can you say some version of that right back at him regarding his trip?
It looks to me like he doesn't really have a problem with how you are behaving day to day, and in general, you don't have a problem with how he's behaving day to day. But each of you want the other to feel and think something that you don't trust is happening and don't think you can be happy without. And each of you want 'evidence' that that feeling and thinking change is taking place. Now I've got much more sympathy with your need than I do with your husband's - he's continued being dishonest and the business with the mementoes seems like a dramatic and silly gesture - just like this trip. I think he's addicted to drama and big events and is trying to replace the AP with the trip. And I think you're right to let him get on with his life and concentrate entirely on yourself, and tell him you're not yet ready to collaborate with him because you 'can't fast forward to that place' (use his words - let him recognise what you are doing).
But more generally, I think you're both supplying the same energy to this dynamic - in that you want the other person to think and feel a certain way, and provide evidence of that thinking and feeling in a change of behaviour. I don't think that is necessarily unreasonable, but there's so much pressure on this - your husband communicating in all kinds of ways that he won't be okay, he won't be happy, he won't be faithful - unless he gets what he wants from you - and I think in some ways you are doing the same back - you won't be okay in the marriage, you won't be committed - unless you get what you need from him. There's a lot of bargaining and this is why you are stuck.
My feeling is that you won't resolve this without a separation. He doesn't seem to be able to leave you alone and sort out his own trip, deal with his own feelings, and learn to be okay even if his wife is angry with him, or has hurt him, or is busy with her own life and. not able to spend as much time as she once did polishing up his ego and participating in his adolescent fantasies. I think he will work on you to provide that 'supply' forever - because even if working on you causes an argument, causes upset, and still doesn't get him what he wants, that is preferable to him than looking inwards and meeting some of his own needs and soothing his own ego. I really do.
But as you've decided to stay, and you're communicating to him pretty powerfully that there's pretty much nothing he can do that would cause you to end the marriage (it's a very very parental type relationship, isn't it?) I think the only thing you can do is work on acceptance - he's selfish and dishonest and isn't able to really participate in an adult functioning marriage. He's going to carry on trying to get you hooked into a game where you meet his needs while yours aren't important. You will probably never, ever be able to reasonably trust him while also being clear sighted and honest with yourself. If you can accept those things, I think you will be able to detach from him fully and he'll be this slightly embarrassing presence in the house you have to bump into now and again while you're off living your amazing life. That might not be your destination, but I do think you won't get past where you are now until you go through that gate.