Look up reactive attachment disorder. There is help, but its different from orthodox therapy and is time consuming and only certain professionals even know how ti treat it. But first you need a more defined, complete evaluation and diagnosis.
Actually, if you are in the U.S. have you ever taken him to a neuropsycologist for an intensive evaluation? it is NOT a neurologist. It is a Ph.D psychologist with extra training in the brain and they are the best the U.S. has to offer for diagnosing in the opinion of many here who have used them. A regular therapist and even psychiatrists do not di such in depth testing on every level. They look for abnormalities in all areas of function, not nust development, but that is covered as well.
Your son may also have inherited some stuff from his father...he does have half his DNA. Does your ex have a diagnosis? Personality problems are often inherited. So is mental illness
Attachment disorder is not inherited though. It happens when the first three years of life are chaotic, crazy and include multiple changes and caregivers. The child then does not feel that anyone can protect him and he stops trusting other people and rebuffs love. He thinks only he can protect himself. He only learns to care about himself, nobody else.
Big red flags for reactive attachment disorder are cruelty to animals, peeing and pooping inappropriately and a fascination with fire. Other issues can be sexual acting out on other people, no remorse, anger, violence, stealing, lying even when caught in the act, playing with feces, and acting veey charming when he has to so the we parents look nutty to psycologists and teachers. Doubt he could fool a neuropsychologist though.
I wouldn't leave him alone with the baby for a minute. Keep the baby in your room at night and lock the door. Replace all your silverware with plastic. Lock the rest up along with other dangerous sharp items. if you have firearms, take the bullets out and lock up the guns. Rehome the cat. The child we adopted killed two of our dogs, but we didnt think it was him at first.
I don't want you to go through what we did.
Perhaps he needs to live in residental treatment while he gets evaluated and treated.
Please take care and protect yourself, your baby and your pets. Right now he isn't safe and he is about to hit puberty. That never helps! Call a neuropsychologist They often have waiting lists because they are very good. Although all of his current diagnosis. could mean attachment disorder too.
Regardless pf his diagnosis he has tried to kill your cat many times and has really hurt others...in my opinion I would not let him come home. He is very unsafe.
Do you have any support system?