Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am very sorry to know about this overwhelming situation. It is very serious since each of them are reacting in very dysfunctional and abusive ways.
Both are adults but if your son continues to live at home depending materially and financially of you, then he would need to come to terms with the fact that he cannot continue fighting with his father and perpetuating this crisis. He is not a child, thus he needs to hold full accountability for his words, choices and actions.
Whenever there are abusive words, or any form of violence, whether it is verbal, mental, emotional or physical, everybody involved must take responsibility for the role they play in such destructive situation and work on changes. If unable to make things work, professional support should be considered. Again, your son is already an adult, and must take responsibility for his choices and actions, and if he is unwilling to cope with this situation as an adult, then he would have to afford the consequences. Your husband is equally responsible for any abusive behavior he has presented, and you could do your best to promote his insight and assertiveness to end this vicious and violent circle, but you cannot control what he chooses to do. Thus your role is to promote their awareness of reality and responsibility, and each of them would decide what they do and want to afford.
This is very concerning and frustrating, but it is reality and you need to come to terms with the fact that you cannot do more than to be as assertive and proactive as possible, setting healthy limits and boundaries, hoping for each of them to do the same, and to consider professional counseling support to work on the individual and family dysfunctions.
Does it make sense?