He sure is addorable, he has the cutest little face and looks so angelic in the pics. I know you can get him back on track if you can keep you're Mom from undoing any progress you make. Keep us informed. One part of my book I read said that if a dog is having any pain at all it can come out as agression. usually in older dogs that might have arthritis or some other pain going on.
Best wishes, keep up the great work.