If that doesn't work, tomorrow or the next day, get yourself a can of CO2 or freeze spray for athletics. heat the outside of the chuck mount, then spray your freeze juice on the inside of the spindle while the weight is on it. it may take a few minutes for the cold to soak to the outside, and for the heat to expand the mount.
I don't like the idea of one jaw being torqued. Still like the idea of using something inside the jaws being tightened up on, and wrenching that. But we each make our own decisions. I wish you success. I had one real bad time on a 9" lathe, when I turned it on before the chuck was all the way on, and it hammered it on... took me a long time to get it off. That's when I learned from the group here about not using the back gears.