I cut mine with a bowsaw handsaw, but the saws all would be easier.
I doubt that weight of ball matters much, they all are 12-16lbs, and then you put a vise on top. Mine is a small drill press vise as explained in the Blade magazine.
The way the ball sits on the ring (tire), weight of ball would have little to do with stability.
I found a round plastic trailer jack wheel chock, but a tire would work fine.
Dan