My guess would be a little hint of a prop....combined with overall OT from short naps and unsettled nights. So he probably jolts awake but in the car the containment of the seat and engine noise/vibration is just enough to help him carry on sleeping. In his crib he jolts and is properly awake, then finds it hard to settle back down again.
If other LOs were not an issue, I'd say do the cold turkey to one nap. My slight concern with that is consistency
as if you're likely to be out and about at times he's likely to drop off (during 2-1 J would fall asleep after 3-3.5h A in the morning in the car, and she was NEVER a car sleeper) or not able to guarantee being home for EBT then I think it could all unravel very quickly.....that said, how's this for an idea?
1 nap days: Reasonable' ie post 6am WU time - nap 11.30, BT 6pm (up to 30 mins earlier if nap very short)
2 nap days: Very EW or accidentally falls asleep early in car - max 20 min catnap then PD for second nap around 3-3.5h later, BT max for 13h day so something like WU 5.30, nap 9-9.20, nap 12.30/1 and bt 6/6.30pm
Late nights - can't be helped - you'll maybe have to revert to a 2 nap day the following day if you don't get a reasonable WU time but I would say if WU still post-6am try to do one nap
Also just wanted to offer a hand to hold when and if you're ready with the night feeds. I know you know he doesn't need them, but I understand your reluctance during teething. You have to be ready hun but you can totally do it. It may not solve your NWs (they haven't all magically gone away here
) but at least you'll have ruled out hunger or a feed to sleep prop as the reason xx
And play it by ear?