You have my sympathie! I habe been battling this pest for a long time in my nano 21 gallons and it's VERY persistant. The turbo snails goes on a rock and eat the thing as much as they can but this pest seem to always avoid them in some spots, then it detach and recolonize.
The mexican turbo does eat it though, but you would need to first clear it up a bit because the dend forest that you have right now is no match for turbo snails, unless you put 20 of them maybe? I am not sure they actualy eat it when it's that long either?
I don't know if high magnesium will help with this algae the way it does for bryopsis?
The slightest bit that detach is going to anchor itself somewhere else and grow like weeds
If you can cover some of the rock for light or take them out and give them a good scrub, that would help. YOu seem to not have much coral so maybe you can take out the rocks that have no coral and give them a good scrub with a brush in saltwater at the same salinity as not to kill the good bacterias and that will help.