Why do I have to continue to compromise? Every time I do, he comes up with another petty issue to argue. It truly seems like he just wants to kick the can down the road forever to avoid having to sign a new agreement. When does it end?
Does anyone have any advice?
Same advice as others. Document. Stay consistent. Don't take the emotional bait.
I also see a lot of speculation from others on your X's thought process, which I think is completely counter to DB principles. "He's thinking this, he's doing that, OW"... this is what I meant earlier about villainizing. I don't see you doing this in your posts, but I hope you don't fall into this trap. It is not detachment. It may help motivate you with anger or help you stay strong but it is not really what DB principles (as I understand them) teach. The ONLY reason I think the WHY could matter is if you are trying to understand his motives so that you can come to some sort of compromise on an issue. Otherwise... waste of mental energy.
I spoke with someone this year who D'ed his W with a small child. She pestered him with constant legal filings and actions for 16 years. Maybe it will never end.
I hope this doesn't happen in your case. The fact is, you can't control when it ends. You CAN control how you handle it and compartmentalize the insanity your X brings into your life into a tiny little box.
My X and I are in a similar endless loop over every little thing it seems. Although I would like to hope a finalized D will end the conflict, I am prepared for that not to be the case.