IAAL, I was a spanker too, I spanked him right into honor roll by the end of second grade. At some point the spanking and yelling has to stop, it shuts the kid down and NOTHING get's accomplished and the relationship suffers.
I also have a constantly threatening, bad mouthing, behind the back game playing, put our son in the middle ex. Should I medicate our son because of that? Hell no. I'm going with what's working. I have done everything I can think of except for removing him from our son's and my life completely. He threatened custody when I fail at this and it's all my fault anyway. Here, let me lay down so you can kick me again. I was diagnosed with ADHD but never medicated.
If you have any better suggestions on how to deal with my ex and how to stop his bull**** I will be more than welcome to hear it because yes, the biggest part of our son's problems are his parents. I've been doing what I should and need to do. I've been here working with him day after day for years. The only ammo I can go with is building a board of professionals behind me and our son to help him get through life as best I can help him, how easy will it be to prove psychological abuse without dragging a nine year old into court? Did I say psychological abuse? Yes, bite me.
btw, never read Dr. Spock, heard he gives a nasty neck pinch that'll put you out like false teeth at a bingo parlor.
stealth, picking up the dog dirt was my son's first chore, had it for 3 years. Caught him singing "what a wonderful world this would be" while doing it when he was 6 years old.