Moving the sub won't help you. He needs to just turn the bass down, I have to run my system subless because I don't want to annoy anyone, my floor standards produce enough to enjoy a film.
IMO you have 3 options
Assume he doesn't know and tell him. Within his room the bass will just feel part of the film, he might not realise how far the low frequencies travel.
Put up with it....providing your awake it's just noise.
My friend had this issue with a neighbour and asking him to turn it down didn't work, I took the 2 x 18" drivers I have for my cinema room and played 17hz non stop for 3 hours each night.....he then understood why my friend complained.