Hi there, Bob,
If you MUST remove the chuck from its arbor, I suggest that you first open the chuck jaws fully and look at the very back of the opening.
There used to be a fashion to drill and tap the end of the arbor and drill the back wall of the chuck to permit the fitting of a securing screw, say 4 BA. The hole in the back wall of the chuck was tapped with a larger thread to permit the use of a suitable screw to push the chuck off the J6 (or whatever) taper.
I seem to remember that this scheme was recommended in one of the Duplex books; Jacobs chucks didn’t come from the factory so fitted.
Should your chuck & arbor happen to have been modified this way you’ll obviously need to remove the securing screw and the push screw might then avoid the need for the wedges. I guess you might still need the penetrating oil.
I hope this helps,
Best regards,
Swarf, mostly.