Hiya lovely, I have to say I agree with Katherine hun, I think we're back where we were a little while ago. My DD had also given up her nap completely at around 28/30 months. I do feel that your DS has possibly been UT for quite some time, resulting in those earlier and earlier WUs. Yes he may be OT now but the way out of that is to reduce that nap.
My DD didn't cope with nap capping so we kept the nap long and for as long as we and she could cope with let her nap when she wanted to, but not otherwise. This did mean we had to accept the reduction in her night sleep. There did come a time where the shortness of the nights was leading to more OT than was acceptable to her, and I needed my evenings back. So we cut the nap on more days.
You mention that when you've tried NNDs before your DS has become unbearable. How many days have you tried this consistently? I think with DD it was definitely harder for her at the beginning, when she was used to taking the nap, I had to really work to get her through to early BT without too many tantrums. But after a while (a week to two weeks) she had got used to there not being a nap and the nights just lengthened.
It is some months now since you first started getting earlier wakings again, so I think it may be time to try something a little more drastic, like cutting the nap (and if not every day it would be worth trying every other day or more often to have NNDs if you can manage).
I know this timeframe and the 1-0 is so hard, and OT is unavoidable, but I do feel that when things have got to a point where you're not happy nd he's not happy changing something is worth a try.
((Hugs))