Hmm, I guess he could need a shorter A time first thing in the AM...But considering his age, anything less than ~1.5h would be on the really, really short side. Some I'm a tad puzzled there. How long was his nap? I normally try a new A time for 2-3 days before saying an absolute yay/nay, just to give their bodies a chance to adjust, iyswim.
I wonder, though, if he's one of those LOs who like really short winddown routines. I noticed that you started it 25ish minutes before he needed to be asleep; do you think he could have been reacting to the fact that maybe he wasn't tired yet? Some LOs will fuss if they're getting winddown cues telling them they're about to sleep if they're in fact not sleepy. Earlier, I know you said you usually allow 10 minutes for a winddown, so maybe today was just different.
I am totally NOT discounting what you say...I hope you realize that. I'm just trying to get a sense of what's happening on the other side of the screen and trying to rule out all other possibilities.
To answer some of your questions above:
I did extend out the first wake time to 2 hours, but since ALL his naps are less than 1 1/2 hours I am always taking 30 minutes off the wake time so therefore the rest of the day it is pretty consistently 1 1/2 hours (with the 30 minutes for short nap removed). Also extending out the morning awake time didn't help either. He went to sleep quicker ( about 10 min) but then only slept 29 min.
With short nappers, it does tend to get tricky, juggling the Es around the short naps. But what you're doing is right. You just shorten the A time after a short nap to try to keep the OT at bay.
I am beginning to think he just HATES to sleep and if he wasn't ending the day a crabtastic MESS I wouldn't care honestly but he IS so obviously he NEEDS the sleep even if he doesn't THINK he does.
I think he just has a hard time getting to sleep and staying asleep, like it's his body that's getting in the way. My son was a short napper for ~2 months, and like you, I could tell he needed sleep, but his body just wasn't capable of extending sleep on its own.
When is the jolt? I thought it was 20 min, he makes it through that, it is usually between 29-35 and he wakes up. We have been TRYING to do BW since 4 weeks but like I said, he has never been a great napper so it just doesn't seem to work cuz when he wakes up early, it throws the WHOLE thing way off.
They have a series of jolts for the first 20 minutes as they drift off into the deep sleep phase. Then at ~40-45 minutes, they start going into the light sleep phase and try to transition into the next sleep cycle. It is at this 40-45 minute mark that we normally used httj with DS. To be preemptive, we would actually go in at 35 minutes, put pressure on his arms/legs, and shield his eyes. We did this until about the 1h mark. It was long and back-breaking, but it worked for us.
Lastly, two other ideas I had: have you tried a swaddle? Do you think he's teething (my DS was ~5.5mo when he got his first teeth)? The consistent 30 minute naps make me think discomfort-related.
Let me know how the day goes *hugs*