Wow, that's quite a few questions there!
I think most pretty much clarified the resistance questions, but I'd argue that it difficult for most users to tell a big difference between say a 1.8 and a 2.2, it's just not going to make that big of a difference to most people. The theory is that lower gets hotter, higher is a bit cooler...but again, my experience is that it's marginal until you start looking at 1+ ohm difference. Also, the lower the resistance, the more liquid that will get used. Dual coil systems will also use more liquid.
I'll also touch on your issue with dry hits. This, in my perception, was the main reason I hunted for the right setup. Honestly, when I started, all of the various clearos I tried experienced this problem. It wasn't truly until I started doing my own custom builds that I found the issue largely solved. I settled on the Kanger Mini-Pro 2 setup and do custom 28GA microcoils with cotton string and haven't had a dry hit since. Some tips, to help though would be to make sure you're priming the wicks (dripping liquid straight on the wick) and if applicable to your tank, you create a vacuum by allowing excess air to escape.
Many coils can be cleaned with OK results, but it's not usually the most effective method. You can try to soak in Everclear or Vodka, let dry and try again. Most times, though, when a coil goes it's because the wick is shot...which no amount of cleaning will fix. That's another reason I got into rebuilding...was to save the cost of buying new coils. I have about 40 or so that I rotate through and spend a Saturday morning rebuilding a dozen+ every few months.
As for vendors, there's many out there and you probably couldn't go wrong with any of the approved vendors here on ECF. I don't like to play favorites, but a couple of the vendors I'd recommend for hardware are GotVapes and Discount Vapers. There's many others to consider, though, and all have their niches. Good luck!