That could be teething, or it could be a dream, perhaps showing as speaking, my DD always does that when she's not sleeping quite a soundly for whatever reason (OT/teething).
It might be worth trying some meds at BT (and maybe middle of the night as a DF too) to see if that helps.
Otherwise, yes you could push the nap back to 12 going 15 mins at a time, and see if that helps. I think around this time my DD had been napping at 12.30 or later for quite a while as that was the earliest they would put her down at nursery.
You will need to give it at least a week to two weeks before you see if the new nap time makes a difference, to give him time to adjust.
I would keep BT the same to begin with and donNy cap the nap either - but we can always tweak that if you feel he needs it.