I’m sorry this happened - especially coming from two providers, not just one. Your symptoms and suffering are legit and real. No matter what did or didn’t happen. You deserve to feel better.
I don’t think the therapist means harm, but she went someplace she shouldn’t go, at all.
I had a fill-in trauma therapist do something like this once. She tried to convince me a certain family member sexually molested me and I would remember in time. I was in a bad spot and desperate for answers... she had a convincing case. It’s scary to think about now, because I’m 100 percent certain now that family member never molested me. It turns out they were in another country during a time I had behaviors in question... and most of the behaviors turned out to be ordinary kid behaviors! Not ones suggestive of sexual abuse. (I had been through verified abuse, but that wasn’t anything she put together - she totally missed that.)
Psychiatrists are not generally trained much in therapy techniques in the US. There are some rare exceptions of MDs that get additional schooling, but they are by far the exceptions. Psychiatrists are usually trained primarily in diagnosis and meds. The psychiatrist was out of place to reinforce the wonky therapist and say it was your father.
Others have already addressed the nightmares. They are not accurate reflections of suppressed memories. If so, then Jaws has eaten me alive many times. I’ve even died in my dreams in traumatic events that clearly didn’t kill me.
Being the only kid who stands up to your father in the way you did is a pattern that can happen in dysfunctional families of all types. It’s not a for sure sign of sexual abuse. Can it happen with sexual abuse? Sure. It can also happen without it.
Stick with what you know. You may never know some things for sure. You can still heal.