Paws, Heyday is right. My ex had a difficult childhood, which he told me all about. I felt desperately sorry for the suffering he had gone through. I wanted to fix it for him. However, after I kicked him out, he said "I did warn you what I was like". Lundy Bancroft has interesting things to say about this as well - there are people who have abusive childhoods, who resolve to do things differently, who work on themselves, and have the emotional capacity to see that what was modelled to them was wrong, and not repeat it. Your ex, and mine, are not such people. Rather, they would prefer to use their abusive childhoods as an excuse for continuing to display abusive behaviours themselves. In my experience, these behaviours are reserved for their partners, and sometimes their children. Not their friends, or colleagues. And they don't show them towards you in front of friends either - they reserve it for later, when you are alone, in your own home (where you should feel safest).
I told my ex that I wanted to have no contact with him whatsoever other than about the property, after he harassed me by text, email and phone. I totally ignored any contact that was not about that. He gave up and moved very quickly onto his next victim, and I know he has told her all about what he sees as his 'issue'. Poor woman. No doubt she thinks she can change him, fix him, help him, support him to be a better partner and father - but I would very much doubt that. They need specialist intervention over a period of years, and a 100% committment to change. Even then, learned behaviours over a period of decades must remain only millimetres beneath the surface....
Also I don't think he thinks like you - you say you want a "managed" way to ease him off gradually without drama. I don't think he will get this at all. I tried to do this too, and all it resulted in was him thinking that I wanted him back! I think you have to be incredibly blunt and to the point with these people. Tell him how it is. Just say no.