Whoa. Psychopath is extremely strong language. I'm no expert but cutting the whiskers off a cat is hardly psychopathic behaviour. By age nine, if your son was a psychopath, you'd be describing much more disturbing behaviour. But you're not.
Having a child diagnosed with ADD and ADHD probably frightened you. I bet you googled those diagnoses and scared yourself even more. Your pride may be a bit wounded too. Guilt and blame must be in play too. Get yourself some support – a group or a therapist, someone you can talk to on a regular basis to keep yourself steady.
Bear with me a couple minutes. You say your son is "extremely smart" and I believe you. You say he is manipulative and that is a sign of a high IQ. Just as ADD and ADHD revolve around “attention” so do the challenges that come with raising high IQ children. High IQ (Mensa) children are very difficult to raise and educate. Parents are at a disadvantage when their children are smarter than them. Teachers have 20-30 children in a classroom and cannot meet a high IQ child’s need any better than they can meet an ADD or ADHD child’s needs. This puts the high IQ child at a disadvantage in a normal classroom (hence they too are labeled learning disabled).
I suggest you get your kid’s IQ tested – by a professional. If you’ve been seeing a therapist, or psychologist, find a psychiatrist instead. The same person who is treating your son psychologically, needs to be prescribing and monitoring his medications as well – and only a psychiatrist can do that.
I also suggest you focus on your son’s attention issues. The recommendations given me worked. No television in the house. No devices at all. No video games. One computer in my office only (no children allowed). Quiet music – and off it went at the first sign of disturbance. We rented movies and watched together. We worked together to keep the house organized and simple. If things got cluttered, we picked up the whole house – together. We maintained a predictable consistent schedule the kids could count on – not matter what. The kids went to bed at the same time every night, but they we’re allowed to read books all night if they wanted (which they did). My kid’s dad and I took turns tutoring our children in all their subjects. Once they’d learned to organize their thoughts, they studied independently and as a group.
This environment enabled our kids to learn how to manage their thoughts, organize their time, develop their own interests, and acquire good learning, study and work habits. Today, at 30 and 33 years old, our kids still do not have a television (cable), their homes are organized and simple, they still study independently, they’ve earned degrees from top universities, have great jobs and they’ve harnessed digital technology (instead of devices controlling them, their devices serve them).
People are struggling with anxiety, but if someone suggests they turn off their devices, they have all kinds of excuses for why they can’t do that. Nonetheless, I am suggesting you do it. Try it for one month; just remove all devices from your home. Listen to quiet music occasionally but live with the sound of your own voices. At first, I bet your son will be very upset. His behaviour may be much worse. However, if you stick to it, I bet you will see him grow increasingly calm and focused. In fact, at the end of one month, I bet you will be as sensitive as he is to the environment inside your home. You too will recognize the symptoms of anxiety in yourself, caused by devices around you. If that happens, you will understand your son.