This sounds like me and DD at this age. You are doing fine. This will get better, usually around 6 months. It is partly developmental and will pass. Generally your night will tell on your day if it needs some fixing, so the short naps don't seem to be hurting him there. Your A times look quite appropriate, but have you tried another 15 minutes just to see how he does? I would give him a few days to settle into them. You could try feeding LO a but later after waking, maybe an AEASY sort of thing?