You've tried already and apart from anything else your son is also witness to this. He will pick up on all the vibes here, both spoken and unspoken, between you and his dad.
You only need to give your own self permission to leave and there is nothing to rescue and or save here. While it’s normal to want to help someone you love, there is no way to ‘save’ or ‘fix’ another person. Ultimately, all we can control are our own actions and attitudes. You should not act as some sort of rehab centre for such a badly raised man.
Abuse is not a relationship problem.
Abuse is also not about communication or a perceived lack of, its about power and control. He wants absolute here over you and your son.
Make plans to leave going forward; your marriage is over anyway because of the abuse he metes out to both you and in turn your son.
What did you learn about relationships when you were growing up?
What do you want to teach your child about relationships and what is he learning here?. This is absolutely no relationship model for him to be learning from; he could potentially become as abusive as his own father if you were to stay.
Why do you think your son adores him?. I would think he fears him almost as much, if not more, as you do. He is certainly learning from you to be both quiet, compliant and subservient in his dad's presence.
I would urge you to contact both Womens Aid and the Rights of Women asap as the latter can give some legal advice. Enrolling yourself onto the Freedom Programme would also benefit you.