unfortunately it is a not a one way street and you making the changes and attempting to do everything in your power to help him is a good way to go.
In regards to his family there isn't much you can do about it but a friendly reminder and giving suggestions on meal replacements wouldn't hurt either way.
I think it is just that his mom doesn't understand and when she hardly sees him then she may feel like she is on the out side. But just try your best and do what you can to help. If his family doesn't see what is going to happen or want to help then unfortunately that is for them to decide.
good luck
