yeah I wouldn't cut the nap either, besides you said he rarely does a 2 hr nap so often he's getting a 5+ A time after the nap isn't he? we do about 6A before nap and 5 after, actually max 5. But I don't really calculate A's anymore, we just have set times give or take a few min.
Could be teeth as you said. Could it be light or anything waking him up in the am?