You just have to trust that we've been doing it for thousands of years without killing ourselves. As long as you've got plenty of salt and a low pH, you'll be fine.
I've made all sorts of fermented foods over the years, pickles, beer, spirits, bread, etc. Haven't gotten sick yet.
It's really hard to get wrong. The salt kills most of the bad things and the capsaicin and garlic have potent anti-fungal properties which make it especially difficult to mess up. If you remember to turn your ferment once a day or so it'll go very well. (By turn I mean physically mixing the material at the top of the jar down into the depths of the jar and dredging up the stuff at the bottom for a while to sit at the top. This keeps "scum" from forming, but the scum won't kill you and can be safely scraped away without spoiling the batch if it does form.)
It does not. I the camera distorts the colors a bit, but when I made the reading, I had it at somewhere between 3-4. This was also confirmed by simply tasting the brine. It is very acidic.
The experience seems to be that organisms which tolerate high salt won't kill you.[0] Ditto for low pH.[1] And the bacteria in high-salt fermenting produce lactic acid.
In general if it tastes OK and doesn't have visible growths (e.g. fuzz, green or white patches) then it's fine. A lactic acid fermentation will actually kill most pathogens, so it's surprisingly safe.
The yeast and other lactic acid bacteria are coating (and usually inside) the produce, so you don't need to worry a lot about "the right culture". (If you want to be sure, you can collect a starter culture, but that's quite advanced.)
I've made all sorts of fermented foods over the years, pickles, beer, spirits, bread, etc. Haven't gotten sick yet.