I am so sorry you are in this awful situation.
I feel sad for Sal too. He's just a little boy. Am I wrong in that or has all my suffering made me overly compassionate?
The boy needs help and I'm hoping that someone can help him. He is your husband's son and he obviously needs love although I understand you are totally creeped out by his behavior and I would be also.
I think it takes men a lot longer to come around than moms. I have a good friend dealing with that now with her husband and their son who is autistic.
I agree the right therapist is needed for all of you. Maybe having him stay at grandma's is a good idea. At least until you sort this out or something.
Hugs to you.