I'm just getting to the end of the years on hormones, and I know where he's at!
All I can suggest is
1. Be sure not to have more covers / thicker duvet than he needs.
2. He needs to learn to respond instantly to the hot flush, by turning back the covers. In my experience, the longer you leave it the longer it goes on.
3. Get used to it. Sounds brutal, but it's not! They tend to last about 4 minutes. The trick is to roll your eyes and start counting off the seconds. You rarely get to 240, but if you worry about it, it seems to last forever.
I found that once I lowered my expectations of a good night's sleep, things leveled off, and then started to improve. I still get at least one a night, but I'm usually sleep before it's over. In fact my biggest problems are waking up cold a couple of hours later!
Hang in there!
-- Andrew --
"I intend to live forever, or die trying" - Groucho Marx
Different reason but I invested in the stain cool to help with monopause hot flushes.
It has a remote and I have it my side of bed and pop it on as soon as I feel the heat starting which wakes me up .. I only have it on for a very short time and remote means I don't have to get up and down.
It might help.