Hi Sonia,
Sorry it's taken so long to reply to your post.
Your A times are about the average for his age... how is he when he wakes from a 40min nap (happy or crying)? Does he know how to put himself to sleep independently?
My question is when shud i put him down again after a 40 min nap to avoid OT.
If he wakes up and is quiet, I would just leave him in the cot for another 15-20mins or so to see if he will put himself back to sleep. He is probably still learning how to transition in between sleep cycles and this is something that takes time. For some babies, short naps are developmental.
Could you please post what your day looks like and include feeds, etc... When he wakes at night, how do you respond to him?