If that doesn't work and you still need to get it higher, wet and fold a piece of paper towel and lay it over the sponge. If that still doesn't get it high enough, dampen a washcloth and lay that folded up in there too. I've had to do both a couple times. Good luck with your hatch!
I've read that you can seal the cracks with candle wax. If you leave them go with cracks, the bacteria might get in, rot the egg and then it can explode in your incubator.