I think the short night may have been overtiredness, but it was a night waking not the start of the day. Problem being that he has been used to it being 'ok' to wake at that time or just a touch later for quite a while now so may well have been hard for him to settle back off. I can't say if it was the NND or the very long nap day which was the issue though.
You messaged me a couple of questions so I hope you don't mind I'll answer them here - it may just help another person struggling in a similar way to yourself.
When you went ct to no nap with a 6.30 set bt, what happened when you had 5am wus and couldn't keep J in her room til 6.30? How did you nanage with the ot if she couldn't do long nights?
How long wd you wait before back tracking?
If we had an early WU from J then I treated it as I would any other NW. She was never and has never been allowed to start the day before 6.30am so I went in if she needed me, reassured, made sure she had her lovey, quick cuddle if needed, tuck back in, told her it was night time and I left. That was enough maybe 9 times out of 10. Sometimes I had to go back in but not often. She didn't always go back to sleep, but mainly did. We also used a gro clock-type thing and she knows she can't get up before the clock goes green. In my mind there is no 'can't keep her in her room' - she does not come out until 6.30am, even if not sleeping, tantruming, whatever because I am the parent and that is the rule I set. That's not meant to sound harsh or like 'tough love', it honestly is anything but as I would always respond to her need for me. But I would not change the rule because it was difficult to stick to, that would be allowing her to be in charge of the situation. Does that kind of make sense?
How did we cope with the OT? We gave her every opportunity for sleep so sensible BT and not allowing her up before 6.30am. Then accepted that choosing to sleep or not was her responsibility. If OT caused NWs or EWs we dealt with them as above. If it manifested in challenging behaviour or tantrums we handled those as normal, bearing in mind she was tired and that was likely the root cause. We empathised (yes, you are very tired, it's hard to listen carefully when you're tired isn't it? Etc etc) but still enforced whatever rule had led to the situation. We also tried to avoid predictable triggers eg taking her round a busy supermarket or something when she was exhausted. If she was clearly tired or had missed out on quite a bit of sleep we would also allow a 15-20 minute car nap in the afternoon (3pm ish was quite a good time for us) and usual set BT. But we found when she was consistently doing NNDs we usually got a 12h night, even if it was a bit broken.
Back tracking.....well I think that's an individual decision. At this point when things were messy we stuck with the set BT plan and decided to see it through. We did similar with the 2-1 when it felt like nothing was working, did set nap and BT and rode it out. So for me, once I'd decided the nap was going, we didn't back track other than the mini catnaps in the car as above.
I just picked up my copy of the BW for toddlers book and I wonder if you might find reading (or re-reading) chapter 8 about time busters/sleep deprivation helpful? The are some good case studies and a plan for objectively looking at things to help you think it all through. (((Hugs))) x
