Heating musts is a total waste of time, effort and energy. It seems to come from out dated recipes and beer brewers who don't know better!
Pasteurisation is a technique developed to prevent contaminants of a biological nature from transferring harmful infections. Which aren't found in honey. Beer brewers use heating as part of the starch conversion (as I understand it).
If the honey has crystalised, then just mix the target weight and volume of water and honey, and leave it overnight. Then just stir the hell out of it to mix the last bit and aerate the must........