Your ex terrorized his son, made him fearful and contributed towards your son developing the shakes and problems walking. Your son/his son still has these problems. He also told you his biggest fear in life is his dad. (detail removed by moderator) This sort of behavior goes deep into somebody’s soul. Your boys will have suffered from trauma, they have had a similar domestic abuse that we have had. They need protecting and they need to heal from all that he has done.
All of these thoughts that come into your mind and things that happen are natural, i suppose it is the mind processing everything. I expect your boys have memories and experiences with their father this is natural too. you can’t just erase someone like that after they have been in your life for years. Your boys will work through all of this. Was there any more news on the community support for them Betterdays? to get them out doing fun positive things, a group of lads that I know have recently gone on a camping & moutaineering trip in the Lake District organised by the Council. I bet your boys would so much love that. X*X