C.N.
Well my first response is not very nice- but in the end he(as you already know) he needs to GROW UP! What do his parents/friends say when he is out all night? They accept this behavior? That in and of itself is not right.
If he was to move back to his parents and she doesn't go with him, how is that different than what is happening now? Is she worried about losing the financial support? Is she worried about losing him? She needs him to start worrying about losing her- not texting him all night to let him know she is waiting for him. She needs to be the one to set this situation straight- and you are her support. Being careful not to make her feel terrible about being with this person but letting her know that you have her back and that you will help her and this baby get through this.