Both solutions are the same as for non-physics, just with pXent_movechar instead of c_move. Move the player upwards when on an elevator, and also for jumping. I can't tell you why it jumps wrong, though. Maybe the gravity is too high. You can look into the many walking examples in AUM or on the resource page - most contain jumping code.

http://manual.3dgamestudio.net/pXent_movechar.htm