I just suggested the 5h morning A thing as when we were starting to hit the 1-0 DD would sometimes go down at nursery for a nap way earlier than I'd have expected. She wouldn't necessarily sleep long, maybe an hour to an hour and a half, and I'd keep her up until near-normal BT, but sometimes it reset things if she was getting OT. Just a thought - maybe try it as a one-off?
We had to cap nap to 1.5h just before 2nd birthday. 2h naps did cause UT at BT but for us it was messing around, not EWing that was the result. With capping to that length DD was fine with 4.5h A before BT. I think though long-term if you're pretty convinced that the last A is the issue for you, then you'll have to try an earlier shorter nap and hope that solves it. Sorry I don't have experience with that other than the odd day or two - never did it consistently.