Cathy, I just wanted to pop in b/c some ideas came to mind. I hope you don't mind, Corrina.
I believe Tracy recommended a limit of 5 hrs of day sleep. I'll try to find that to double check. I have a feeling he may still be on a 24 hr clock since he wakes that same in the night as he does the day. My suggestion would be to try for a 3-3.5 hr feeding rountine b/c this would add an extra feeding in the day time. Even though you say he takes less, he'll probably total out the same by having an extra feed. He's taking larger feeds at 4 hrs b/c he's more hungry. Secondly, I would limit his naps to 2 hrs, and his last nap of the evening being a catnap of 45 mins. Then, I would aim for a bedtime 12 hrs from the morning wake time in hopes of resettin his internal clock to a 12 hr day/night pattern. Of course, night wakings for feeds would still be common at his age.
Here's a link that might help to get you started. As for total A time, including the time to feed, it would probably be up to 1 hr.
https://babywhispererforums.com/index.php?topic=62100.0