Good questions!
First.......the process of galvanizing steel reqjuires 830 degrees or more, so a gasoline fuel wood fire of 500 degrees or less wouldn't affect it. Repeated exposure to heat in excess of 450 degrees will eventually crack the zinc layer of the galanizing, causing it to peel. Underneath, however, will be heat-treated steel which may be unnoticable until it rusts.
Second, accelerants such as gasoline and motor oil make a fire flash hotter for a few moments. The rapid increase in heat creates a chimney effect, with the heat convecting rapidly upwards, not radiating outward.
If you have ever stood around a campfire on a cold night, the last thing you want is for someone to throw accelerant on the fire.
Third, I don't know why a corral would be padlocked, but I caught a glimpse of the padlock on PF's gate, in the video of him telling reporters to get off his property. I was the best Master model. Weatherproof, bullet resistant and heat torch resistant. If he had a padlock hanging close to the fire, it probably was unnaffected.
Fourth, I believe that "scooped up" meant he used his Farmall type loader to lift the entire trough and load it in the back of his truck. Western ranch people would never say "scooped up" to mean "scooped out" as with a hand shovel. Once he dumped the contents, it probably could have been cleaned thoroughly with a worn corn broom. He may have simply returned it to the ranch, or left it on his leased land.
Finally, I am extremely skeptical that he actually burned KB's body. The description Investigator Slater gave just doesn't seem big enough, or of sufficient burn time, or the right odor. I think it could be that it was all of the other stuff that they removed after cleaning, plus the purse, all stuffed in the tote. I think KKL was conviced that she participated in the burning of the body, but she never actually handled it. I think that might explain why they found chunks of charred plastic, but no human ash. Why would he bother to do a thorough cleanup if there was no possibility of tissue match from any residue?
IMO