My son's dad is causing him trauma

My son (14) is in therapy because of his behavior. He has a lot of anxiety and paranoia. One of my friends who is a therapist says he shows signs of sexual abuse which terrified me. He's been seeing his therapist for a couple months and his therapist asked to meet as a family with my ex a few times. He asked my ex some questions about his past and stuff like that. My ex actually was sexually abused as a child and him not learning to heal is what took a toll on our marriage. I met with my son's therapist this morning and he told me that he doesn't think that my son has trauma or was sexually abused which is amazing to hear. He said how my son mentioned living full time with his dad for a few years until we moved closer and now it's split custody. He said that he thinks my son is experiencing a type of secondary trauma symptoms from his dad. The behaviors he's experiencing are learned from his dad who is paranoid and seems to have problems trusting people. We talked about it for a while. I'm glad my son doesn't have any trauma or abuse but if his dad is causing him to act like this that stresses me out. It almost makes me want to try to get full custody. My mom says I'm overreacting and to just let my son do his therapy and learn coping skills. I just want my son to be safe and mentally healthy and it's frustrating to know he picked up all this behavior from his father.

@R thx! I'm thinking about getting a lawyer because we live in a 50/50 state and with my son being 14 the judge will ask him and I know he's gonna say he doesn't want to be with me full time. The only reason his dad had full custody those few years was because we came to an agreement that it was for the best for the time being.