Hi Lulu.
I am so sorry, especially for your hurting son. Of course he is hurt. I am sure he is lashing out hurt at you because you are safe and accessable, while dear old dad is not even around. It hurts you, I know it does, I am sorry. I think that is how kids handle absent anyone in their lives. They are hurt and have no other way to let it out than to let it out to the people who love them the most, and we are not to be offended. He is lucky he has you. You cannot change dad. I am sure you would have a million times over if that were possible. One day your son (unless he already has) will realize all of this for himself. It does hurt but with one parent to guide them properly they can get over those hurts too and see they too did not cause it, cannot control it and cannot cure it.
Gentle hugs my friend.