Its always so hard to know whats going on with our bubs.
My DD is 11.5 weeks, just the last few days she has started having longer naps. She was also a cat napper having on average 45 min sleep. She still does but as I said the last few days she has started haing 1-2 naps a day that last from1.5-2 hrs! She started doing this all on her own.

The thing is you said your son can be grumpy when he's awake so I think maybe he needs more sleep. I didn't worry too much with Ashleigh because she'd always wake ready to play and smiling and kicking around that there was no way i could settle her, although I did try for a while cause i was told by "experts" that they have to sleep longer but she would just cry and then she'd be due for a feed and we wouldv'e wasted alot of time. If your son seems happy I don't see a prob getting him up, maybe just put him down after a shorter play? I do think 20mins does sound bit short, is this when he tends to get grumpy? Do you try and resettle him and what effect does it have?

In regards to the feeding, maybe he is more sensitive to wind and could that be really upsetting him? I know occasionally Ash will be really upset during a feed and I will stop and hold her upright for a few mins patting her back and often this will settle her ready to continue.

Maybe ask ABA for advice on the BFing and ask you MCHN for some advice? Just remember though that all babies are different and you will gets lots of advice from experts but you should do whatever works for you and your baby.
Good luck.