Yes, I'd definitely increase his A times. Most LOs his age are doing 2h15-2h30 of A time...your LO is only getting 1.5h. He takes a good morning nap, but that second nap, I bet he's fighting it because he's not tired enough to go to sleep yet, or take a long enough nap.
When our DS was doing 2h15 A time, this is what his routine normally looked like:
A: 7
E: 7:30
S: 9:15 (2 hour nap)
A: 11:15
S: 1:30 (1 hour nap)
A: 2:30
E: 3:30
S: 4:45 (30 minute catnap)
A: 5:15
E/A:
S: by 7:30
Since there's quite a big difference in between where your DS is and where he needs to be, you shouldn't make this jump all at once. Start by gently extending his A times 5-10 minutes (15 minutes max, if you know he can handle it). I've found that going for a walk or softly singing songs/looking at books, are great ways to help them extend (you'll want to keep the activity low-key so that he doesn't get overstimulated). After 2-3 days, extend again. Keep extending in this pattern until his naps and his night sleep get better.
While it's true that some LOs are high sleep needs babies and therefore have shorter A times, it's usually not an hour less...maybe 15-20 minutes.
As you help get him used to the longer A times, his sleep will sort itself, but I wouldn't let him sleep past his E time.
So, try that out for a couple of days and let us know how it goes!
