Hey sorry I had this thread sitting in my unread but never opened it for some reason.
You could try out this virtual controller: Hubitat Enhanced Virtual Fan Controller · GitHub
It originally came from the author of switch bindings. I was working on making it universal for any speed but as of right now its setup for just 3 speeds, low, med, high, which is what it sounds like you want. If the speed <-> level conversions are not working to your liking it can be adjusted pretty easily in the code.
Then I have switching bindings setup like this to keep it in sync with the actual fan device
[RELEASE] Switch Bindings 2.0
