Am i neglecting ds by allowing this kind of rough angry behavior of his father go unchecked.
Yes. You are allowing his father to abuse him. That's unforgivable.
His home is unsafe and unstable. He never knows when dad will kick off. He never knows what behaviour will be acceptable today. He never knows if he can relax. His body is constantly in a high stress state. He thinks it's normal to be bullied and hurt by people who claim to love you.
He is 8. A fully grown adult male roughly dragged him out of bed. How is that better than being hit?
He would have been completed overpowered and very, very aware of how powerless he was to defend himself from someone so much bigger and stronger - and who at that time was being aggressive, threatening, and was assaulting him.
A child's assessment of the threat to their life in such a scenario is different to an adult's. Because a child is much more vulnerable and less able to protect themselves. A child in that scenario would have been acutely aware that the adult could easily have seriously injured or killed him - and that the child could do nothing to stop them.
It would have been absolutely terrifying.
And to have his mother sitting back making excuses because she's decided he's not worth protecting from the abuser in his own home?
The damage this has already caused over the last eight years is significant. The lifelong damage and destruction it will cause if you continue to allow him to be abused for the rest of his childhood does not bear thinking about.
Your child is already traumatised. Stop making excuses for his abuser and stop pretending that you're staying to protect him from the so-called "trauma" of divorce.
Look up the Freedom Programme. It covers how children are affected by being forced to live with an abuser, and how they can recover if the abuser is removed.
He is an abuser. Stop making excuses for him and protect your child from him. It is very distressing that you have allowed your son to be abused like this.