His A time is usually between 1hr45 and 2hrs and I always WD around 1:30 so that he is not over stimulated, I always go by his sleepy cues too. I don't mind APing as long as he gets his sleep as he is much happier on his awake time!
I found that when I was having trouble with his naps before it was because I was putting him down too early, he is much better since increasing his A time.
If I leave him, he just cries unfortunately and gets upset. Today for example he woke after 40 mins, I tried to get him back off which didn't work, so got him out and gave him a cuddle for about 30 mins then he went back to sleep on me.
When he does wake early, he is quite happy to wait an hour or so before his next feed so I don't think he needs extra food.....he is teething too so prob doesn't help!