I can identify a little with Maca because I tend to do the same thing when I am struggling with something - I am ok with it in theory and then when it's happening in real life I have a harder time dealing with it. In my brief and disastrous poly relationship I ended up with a big difference between how I *wanted to feel* and how I *felt.* Is Maca like that about other things as well? I would not be surprised if this is less of a poly thing and more of a general difficulty he has in processing emotional responses and having realistic expectations for himself and what he can handle.
For what it's worth, I have done the back and forth thing for more than 14 months (not about poly)... so I can sympathize with Maca on that too. And from seeing my fiance having to support me through that, I can sympathize with you too! Some people just take a long time to process things, I think, but I don't think this length of time means that he will never get better or come to a more favorable resolution.
Anyway, I wish you all the best in figuring this out.