M.L.
I would tell him to get over himself and give his dying mother a phone call.
So what she is a downer, apparently she has a reason to be b/c he doesn't seem to care about her or take initiative to call. She may be a beast to deal with, (I have family like that), but she's at the end of her life, and it's time to put those feelings aside.
His mom may be happy you call, but that doesn't replace her own son rejecting/ignoring her.