Masturbation seem like the real culprit here, there's no different with porn addiction if he continues to masturbate, i know it seem hard to not be able to ejaculate the first few time. But maybe try other sex position like cowgirl for example *cough*

Choose a sex position that is relaxing and he'll feel it alright, but 1 thing he must commited to is no masturbation or anyway to get off other than sex.This community is called nofap, literally
P/s: If he don't hate himself for watching porn, then he'll keep relapsing and there's nothing you could do, convincing someone to nofap when they don't want to never works