Looking at your picture, and with no experience with this part, is it possible to "tap" the piece that you are removing parallel to the transmission rather than perpendicular?
The set screw is removed and there is a round shaft in a round hole. I am guessing that if it were all cleaned up, greased, and no set screw, that you you would be able to spin your part around that shaft. Maybe tapping it in a parallel direction in reference to the transmission rather than perpendicular, it might help to loosen it to get it off.
I do not know if there is anything you could damage by tapping it in this direction. If it were my car and I was working on this project I would try it. Transmissions are usually reasonably durable.
I've seen you post here with no help, so I thought I would look at it a little better to see what I would try next if this was my project. Let me know when and how you got it off and if this idea helped at all.