Tony, I don't know what temperature is the max, but I can probably find out. I have been told of instances where burnishing with leather has melted strands. You can contact BCY directly about this if you prefer. Normally I "could" be wrong, but in this instance saying Dacron can be damaged with heat is like saying gas can catch on fire. Not much chance of screwing that one up.
All current modern string materials are, basically, plastic fibers (some blended with LCP). Plastic melts when you get it too hot. The hotter it gets, the more pliable it becomes. That's why Dacron and 100% HMPE strings tend to "creep" in hot weather.
Rob is spot-on. String wax is a lubricant, and if anything saturating string material with wax will cause it to settle a bit more, as the excess gets squeezed out.
Bee's wax hardens when cooled. At best, it's going to get shot out of the string in short order, and heating may remove the factory "wax" (normally silicon based, so it absorbs better). If anything, the heating could cause the string to wear faster due to the silicon wax being melted out (much lower melting point than bee's wax).
I know the question was asked of Rob, but here's my input. When/where Dacron will "take a set" depends on a few variables. Under the right (wrong?) conditions, it can keep on stretching until it breaks (high temps, low strand count, heavy load). Or, under the "right" conditions, it can settle in (enough strands, light enough load, temps not too high).