What a terrible shame this has happened to your boy,my DS1 and his then partner split up when their bay was 18mths old and I'm sure that as long as his name was on birth certificate (it was) he could apply for parental rights giving him over night stays etc and 2 days a week access on their agreed terms,I'm not sure if things have changed there is sure to be someone along soon to tell you the up to date stuff if things have changed.
He is not required to pay maintainance before the child is born but there is nothing to stop him buying necessities if he feels he should in fact it would work in his favour I think,I hope things go well for him keep us updated please.I wouldn't mention overnight access at this moment as x girlfriend will be feeling very hormonal to say the least leave until well after baby is here when she can be discuss things rationally.