To the OP spoilage or mold is easy to determine with your nose & eyes. Botulism is not until it is to late.
Bot doesn't grow well in the presence of air, so it forms tough shell-like spores and hibernates until conditions are right. The spores are commonly found in the environment all around us. But they are not a problem unless conditions allow the spores to germinate and produce deadly botulinum toxin. Clostridium botulinum prefers anaerobic (oxygen free) conditions. So submerging meat in water for days is rolling out the welcome mat. Example; you marinate that jerky for several hours in the fridge submerged in water. And cooking the meat when it comes out is no guarantee of safety because the spores don't start croaking til the temp hits 250°F or so. The good news is that the Clostridium botulinum that emerge from spores are much more sensitive and they die at about 175°F and the toxins they produce are inactivated at about 160°F. You might ask, why not dry cure, in air rather than in water, but there is little oxygen deep in the center of a slab of meat, so Clostridium botulinum spores can hide and grow there.
I'm far from an expert, but I have spoken with many who are. As well as studying the subject enough to know that I will always use a curing salt (Prague Powder #1) in my cured meats (Jerky, sausages, corned beef, and bacon). I always use an accurate scale to weigh my product along with a Wet Cure Calculator.
The Science Of Curing Meats Safely
Also, I do not recommend using a dehydrator to cure your Jerky. Most and including mine (Cabelas Commercial 80L) will not run hot enough to bring the Jerky up to an internal pasteurization temp of ~160. I use our oven or smoker set at 225-230 along with a high quality meat thermometer to bring the jerky up to 160F internal. I only remove meat from the cure as my oven or smoker space will allow. Once the internal temp is achieved, I move the meat to my dehydrator to dry as desired. It could be left on the smoker at a lower temp once reaching 160F, but I usually work in batches of 25# and my smoker isn't big enough to accommodate that much meat at once, but the dehydrator is.
I whole heartily understand & appreciate your concern of Nitrates and/or Nitrites. All of us consume them every day, even if we eat vegetables straight from our own gardens (celery, carrots, asparagus, . The fact of the matter is that they are not the big boogeyman, and we will continue to use them in our house.
Here are a few other sources of reading on the subject. My brain cannot comprehend all of the science, but I can understand the overall picture:
Collaborative Research paper completed by Baylor, Mount Sinai School of Medicine, EpidStat Institute, and Coughlin & Associates
Ingested nitrate and nitrite and stomach cancer risk: An updated review (PDF Download Available)
World Health Organization
Nitrite (JECFA Food Additives Series 50)