I would stick with distilled. Reverse osmosis (RO) forces the water through a semi-permeable membrane to remove impurities. The membrane pore size determines the size of impurities that are removed. However, there are further steps that should be used to get truly good water, like a carbon...
With modern sealants, like Blackfire, it really isn't necessary to add wax over the top. The only thing that goes over the top of mine is a good car cover.
I hope you aren't in S. FL. I'd hate to go to this guy! Wonder if he's been sued yet because of the damage the old guy did. If the old guy was so great, why isn't he still there?
Don't agree to anything a third party writes for you. Tell him no, you are a detailer, not a licensed mold abatement specialist and you did what was reasonable in your industry for light surface mold, anything beyond that will require a licensed abatement professional to determine the validity...
Walmart also carries a line that is blue on one side and a tannish/gray on the other. They are really heavy, buff OK, but don't absorb water worth a darn. I use one as a pad under my arm on the center console. It's great for that.