Please, I do not have "All" or possibley any answers. Remember with living animals, answers are the result of doing something. Not the doing of the something.
I believe I was the one responsible for so many people using and misusing dirt. I recently read, that there are over 2000 kinds of dirt. There is the problem.
You can research the kind of dirt that the species you are concerned with, is adapted to. Most monitor species are particular with very certain kinds of dirt. Savs, are not different. They understand certain kinds of dirt. Your job is to find out what is the makeup of the dirt they prefer.
Most arid land monitors, perfer dirt that is, poor in quality, that is, lacking decomposing plant matter. The arid soils are more alkaline as opposed to, acid.
So to say the dirt where you live is good, I cannot. I have no idea what your dirt is like. You should read up on their habitat, I believe many books include perferred habitat, and type/s of soil.
About disinfecting the soil/dirt, I do not do that. But again, I have no idea whats in your dirt/soil. Please consider, that they normally live in dirt from the outdoors, heck it is outdoors. I believe it would be far more important to disinfect the dirt after its been in the cage for a year or so. Good Luck F