Just want to put emphasis what other posters have pointed out - if he thinks he is doing "everything" now, but is also so unhelpful that the girlfriend is more than happy for him to abandon her and baby for 5 nights a week then he isn't doing "everything", it's likely he is just being asked to do more than before he became a father and he's got his panties in a twist.
Shock horror, life with a baby is busier, more difficult and requires more responsibility than life before a baby. Mum will need your son to step up and actually parent his child, do a fair split of all household chores and importantly, MUM WILL NEED A BREAK TOO.
What your son suggests means that poor mum does ALL of the weekly night feeds, meaning she gets very little sleep, only to then look after the baby for the whole day, the whole evening, doing all the feeds, washing, bathing, cooking, cleaning, nappies, bedtimes etc, while your son does his job (like every other parent with a job), but then goes home to have 0 responsibilities. He then plans to just drop in and check on mum on the weekends, play disney dad, probably take a few photos to he can post about being a father on his Instagram, and then he'll act all surprised when suddenly Mum doesn't want him back as it's easier not to have a manchild around the house.
I'd be GUTTED if any child of mine came to me asking if I could enable him to back out of his responsibilities and abandon the mother of his child (and in turn, his baby).