Itabull,  make sure that you put his moms ass on top of his pillow before you fuck her.  Then cum inside of her wet pussy and let it all ooose all over the area where his head will sleep.  Make him cry again,  run to his room, and plant his wet tearful face into his pillow.... You can both watch from the doorway where he cannot see you both,  pushing your cock against her ass as an award. 

Ever think of fostering a older boy to help bully her younger son... 

That is an incredible story,  is there any more bad little things that your gf likes to do to her son for her pleasure