Ive got to be honest, I really don't think this is a good idea. 2.5' is a lot to lift this bus and have it floating up in the air. It will be incredibly unstable and very unsafe.
You should really look at any and all other options for getting it closer to level. It might be worth it to try and have the area regraded to a less dramatic slope so you can park on a levelish surface without needing to jack it up every time you move it.
My driveway has a mild rearward slope, (bus is backed in) and my bus leans slightly to the drivers side due to the ridiculous weight of the head end of a horizontal engine, so I will never have a level work area. I just make everything square to the floor and some reference marks on the walls, and it has worked out fine for my build.
That being said, if you are hell bent on doing this unadvisable and ill conceived lifting operation there are a few points you should remember.
Can't tell from the picture if its a RE or an FE, I would not recommend trying to jack up the end with the engine, its very heavy. Or lifting the rear end, because that is where your parking brakes are holding you.
If its a RE, turn it around and jack up the front.
Make sure the wheels that are staying on the ground are extremely well chocked, and unable to move at all.
You will need to support it with cribbing stacks made out of at minimum 4x4 lumber. 6x6 would be better. Cribbing height should not exceed 2x the size of its base, and the ends of the stack should overhang at least 4", I would go with 24" cribbing as a minimum, with 3 pieces in each layer.
You will need properly sized wedges to angle the cribbing stacks to match the angle of your driveway.
You will also need to make and install some sort of struts to prevent lateral movement. These would be long pieces of timber anchored to the ground and extending up at an approx 45* angle to a solid attachment point above the COG, as high as possible. I might even set up a second set low, attaching to the frame.
I have done exactly what you are planning to do, I am a firefighter, USAR team member, rescue technician, and an instructor for my states fire academy specializing in technical rescue. We have trained on heavy lifting operations involving buses with vehicles deeply buried under the rear overhang to simulate severe rear end collisions. However we had professional extrication tools for lifting and stabilizing the load including Paratech rescue struts, Paratech lifting airbags, and an entire forest of cribbing. There was also about a dozen well trained rescue technicians and it takes input from all hands to do it safely and securely.
In short, don't do this, its a bad idea, its extremely dangerous, and there are other options.