Yes, of course you don't feed at night is baby doesn't ask for it, and if he settles back with a dummy then great. But if he doesn't, then I'd put my money on hunger.
One can't know if the 4/6NW is related to him being OT. It could be hunger, it could be change of temp. in the early morning, light coming in, noises in the house, it can even be UT... I know, confusing. But even if the NW is not because of OT it would still be good to keep him awake for an age appropriate time because your afternoons will be easier (hopefully) as it looks like his afternoon and evening are very long right now.
The way you would change a routine when LO is tired due to too much A time is shorten the A times.