Gonna be a bit blunt here but I hear some guilt talking.
Just look back at your post at the hard decisions you have made. It seems to me that it is starting to do what you want - but not the way you and your
DH wanted. Of course that is going to upset you.
You have taken a lot onto your shoulders. First having to deal with his challenging behaviour, and now having to take the course of action that - quite simply - should be the hardest one any parent ever decides to take.
I'd recommend you debrief with yourself for a moment and decide if this is really the way you want to go - and yes do remind yourself of everything you have been through. Once you are better at ease with your decision, you will better handle the fact that yes - this stuff should help change and calm him down.
In the mean time, do not blame yourself for being so desperate. Sometimes it would help to have the support you needed at home, but I guess unless he has actually be through what you have, then he simply can't understand the choices you're wrestling with.