Have you tried using an eggcrate on the mattress? They seem to help with the heat and I know they use them in nursing homes for those who are more bed-bound so they don't heat up so much.
I do suffer from nightsweats and hot flashes and yes, they do wake me and give me a rotten nights' sleep so I can certainly sympathize with what you are going through.
Oh, another thought, I've found that using percale sheets as opposed to muslin seems cooler for me also. The high count thread/better grade sheets seem to work best for me.
Hope you can find a solution!

sabby