To prevent your wheels from coming off the ground try using manual level instead of auto level.
In auto it does this crazy dance back and forth until it finds it's way to level but as it lifts one side then it might go too far so it has to lift the other again and so on...you get the picture.
Solution is to use manual level and get it level without the dance and lifting wheels off the ground. Try that and I bet you will be able to keep the wheels on the ground and level the coach easier...there will still be those times it still lifts too high because the spot your at is so out and a wheel comes off but then just raise it past the level point and add a block or two under that wheel and then start over.
I hardly ever use the auto feature on my jacks and can level a lot faster and keeps it lower all the way around. Try it!