The rate you're going it sounds like you'll pull away the mount on the chassis.
I suggest you cut the mount away from the sub frame mount.
Normally you use a hydraulic press =>
Achtung - Das schweinhund baby benz thread
I understand your frustration - attempting this with everything fitted to the car would make things 100 times more difficult.
Try not to damage the chassis / body. That's harder to repair than the sub frame.