I've cut literally miles and miles of storefront aluminum in the last 38 years with WD-40 and buy it by the gallon. As far as flash point...aluminum is non-ferrous, therefore, no sparking. That being said, the aluminum I'm cutting is generally anodized, which can give minute sparks but again has never been an issue. Does make the guy that welds for us crazy though.
In regard to thickness, as a general rule, aluminum blades for cutting over 1/8" are generally thicker. I use 80 tooth blades for everything and really only lube for 3/16" and up. Don't cut without a backer board, aluminum and plastics will really screw a blade if one of the teeth gums. Take light cuts so as not to fill the gullet. Toolstoday sells Amana and AGE (German) blades for aluminum, including all Festool sizes includng the Kapex.