I have to disagree here. Meth producers know better than to cook the stuff in their own residence. If he was a meth producer he would have known better. Besides, you need a virtual lab in order to produce meth, something that would not have been able to be hidden in a trailer. I do know there is a method for making very small quantities for personal use (they use a 2-liter bottle) but he wouldn't have done anything to her if she disrupted that since making meth in that way only requires shaking the bottle. He could have easily told her to go away without losing his temper.
I've seen a few photos of EK and EW neither of them look like meth addicts to me. They have none of the physical signs and attributes of those addicted to meth. Same with the heroin angle. Neither of them were users I don't think. Again, they lack the physical attributes and if they were using they weren't shooting up. Shooters will hide the track marks, both EK and KW have many photos of themselves in t-shirts. A heroin addict who shoots wouldn't be running around in tees.
My suspicion is that at the most they were stoners, maybe pill poppers.