I haven't got a solution for you with your stuck starter Jaffa, but I can only share that I have had the same symptoms with the other style of Tecumseh starter.
The type where the forked piece of plastic comes through the centre and a plastic wedge holds it from the other side.
I solved that one by shortening the length of the wedge by squashing it a bit.
Once reassembled.
This then gave clearance again, so the pawls could throw out.
