If you want to position your jacks out wider you really need to invest in some proper outrigger jacks, or fabricate some heavy duty ones. You're playing with a heavy load. It has to be done properly. If you don't weld then bring the bus to a welding shop. They could build you some frame-mounted extensions to secure the jacks.
Otherwise use the jacks on the frame. It is narrow, but with properly rated jacks you'd be surprised how stable the bus is when jacked at the frame.
As Christopher mentioned, you shouldn't be looking to lift the wheels, just to take the spring out of the wheels and suspension.