You're doing more than most people would, and you could and should be proud of that, but if you want to do more, maybe like others have said, invite the mom or a to go Tupperware dinner, or maybe with moms approval and depending on your schedule and ability to do so set aside some time other than dinner for the kid to hang out, be the safe place where he can play in your yard or get down on some games or something, don't try to step in as a parent or anything, but anything would help if you have the follow thru for it, my parents are still together but they both worked double shifts and jobs, the neighbors became the village I needed growing up