I'm not fond of storage units at all. I've taken way too many reports of break ins to them. Add to it the problem you are dealing with. I'd be finding a new place for my stuff pronto, no questions asked.
I worked as a narcotics detective for awhile when our meth problem was rampant. I was dealing with labs daily here until we got it under control. Being DEA certified to dismantle clandestine labs such as meth labs I've spent more than my share of time in rubber suits repirators and SCBA's. I've also had some accidental exposures to some nasty stuff and have been very lucky that none of those have caused any type of immediate problems. Who knows what I will end up with in the years to come.
As for meth, depending upon the method they are using to make the stuff, the byproducts can be a serious hazard to your health. Sounds like they were using the Nazi or Birch method which they use anhydrous ammonia for one of the catalysts. Anhydrous ammonia is some extremely nasty stuff with some serious health hazards. The Iodine or Red P or Red Phosphorus method is even more dangerous and can produce both phosphine and phosgene gas, both of which can kill you very quickly.
Many chemicals used are combustible and will explode if ignited. I've worked many an aftermath after labs have exploded. One guy literally had his testicles blown off in one of our local mishaps. Sad thing is his 5 year old son witnessed it and he did not survive due to third degree burns over most of his body. Luckily the kid was not seriously injured and survived but one can only imagine how messed up that kid will be for the rest of his life. I've also got a budy who has a wife that works for Dept of Child and Family Services, she was exposed to meth lab vapors and has suffered from very severe respiratory problems ever since.
Meth labs aren't anything to be taken lightly. If you ever come across it again, get out and get away and immediately make that call to 911 and report it.
As for them not having enough to charge the person involved, I don't buy that at all. I'm not sure where you are at but here in IL just what you have described would be more than enough to build a case on, especially if the suspect has any previous involvement with meth.