Congrats on the sleep in! it does help to feel human again
As for the fights for going down for nap, you say he nods off quite easy in the car, but not at home? mmm... maybe he needs more wind down for nap to stop fighting it? like 30-45 mins of quiet time before nap make it a quiet time, setting some light music on the house, reading books, putting the toys "to bed", eating some heavy snacks prior to it to have calories to stand up for longer awake time.
I found i had to "convince" ds to go to bed. Some days we'd ring neighbour's doors to wave them nighty night
and we'd go out to thegarden to see the squarrels/ants/cats etc going for "their" nap or stand next to the window waving the kids or people that crossed by and id say ds: they're on their way home for their nap... sounds looney but i really got him in the "napping" business.
Good luck, you're doing an excellent job!