Yeah, that A time *might* be a bit on the short side, although if he's short-napping he's probably going to give you cranky cues at around an hour. I'd see if you can gradually extend it by a few minutes here and there, even adding 5 minutes every couple of days gives you a start at pushing those times. And then if you are able to get him to extend naps on his own, soon he'll drop that catnap at the end of the day, leaving you with 2 longer naps and a third nap that might be 45 minutes (our 3 naps were all 90-minute naps once we sorted it), sort of its own catnap.
Also, topping up the daytime calories will help, although you've got the 3-month growth spurt coming up, so don't let it catch you by surprise - it's a biggie!
But if you can get him to sleep thru that 4AM waking, or get him back to sleep before he wakes fully, the plan is that he'll wake up more fully rested when he does wake for the day.