Hi Kerry!
We went through a terrible 2-1 switch around 15-18 months old with DD, and I heard from several other BWs that there is often a regression after 6 weeks of being on 1 nap consistently, so it's interesting that you mention the 6 weeks...
It can take 2-3 months for the nap length to settle down to about 2 hrs consistently. We also had a lot of short naps to start with, it's very common. I think it's good that you're allowing an early bedtime to prevent too much OT from the short/early naps, but I would also advice trying to *gently* push the nap a bit later, to about 12 noon. It was first when I did that that her naps started to consistently lengthen and bedtime could be a reasonable time and wake ups too.
Is he happy when he wakes from a nap early or is he grumpy? That would be a good indication of if he's waking because he's OT or UT.
Try to gradually lengthen A time in am by doing low key activities like reading, watching a dvd or giving a little extra snack.
Be patient! It sounds like you're doing great, he's only 6 weeks into his new routine and it does usually take a while for things to settle. Re the day care, they might also have more success if putting him down a little later. Hopefully, if they're consistent too, he'll get into a new routine at daycare too, but as pp said, LOs do tend to sleep less there and it might take him even longer to settle in to 1 nap there.
With regards to hrs of sleep/day, keep track of how much he's getting and watch him closely. If he seems to do alright on less sleep than before all is well, but if you think he's getting accumulated OT keep giving him earlier bedtimes and you can also do an odd 2-nap day (say once a week) if you think he needs to catch up from lost sleep at daycare.
Hope this can help a little at least.