TeeCat
One-Mik Wonder
You might want to try a plastic dead-blow hammer on the end of the bar. I use a big wooden carving mallet in situations like that. These both apply "shock" but are absorptive as well. Just make sure you're tapping your bar in the right direction, as when threaded things are "upside down" it's embarrassingly easy to get confused. It'll come out. In a worst case, you can at least replace the sump plate. The lower case half, though... not so much.