So the thing about chlorine, and why I didn't have you go that route, is that it is more work, especially when you have an ozonator. The reason is that there aren't slow-dissolving tabs you can use as you do with bromine tabs. Trichlor pucks for pools dissolve too quickly in spas and are too acidic so it's too easy to mess up. It technically can be done, but it's hard and will likely void your spa's warranty if those wonderful guys at the spa store ever found out. So with the Dichor-then-bleach method you would have to add chlorine EVERY DAY because ozone reacts with chlorine so you'll have a higher chlorine demand in between soaks. The good news is that the ozonator will oxidize bather waste so reduce chlorine demand after each soak. It's the in between times (i.e. if you don't use the spa every day or two) that are a problem.
I can certainly help you with using chlorine, but if you plan to have periods of several days, especially more than 3 days, without adding chlorine, then that will be a problem. Maybe, just maybe if the ozonator is on long enough it will prevent the spa from going south, but that's a pretty big "if".
It's easy to go from chlorine to bromine at any time. Going from bromine to chlorine requires a water change. So maybe you can try chlorine and see if you can handle the maintenance and if not then switch to bromine. Does that sound like a reasonable plan?
As for Dichlor chlorinating granules, just get the pure stuff which is usually around 99% Dichlor ("Sodium Dichloro-s-triazinetrione Dilydrate") such as in brands like Leisure Time Spa 56 or SpaGuard Chlorinating Concentrate or Rendezvous Spa Specialties Sani-Spa Chlorinating Granules or any brand with the right ingredients and decent price.
Since you have a Taylor K-2106 you don't have the CYA test. You could probably go without just based on dosing, but if you want a test you can get just the
CYA test from TFTestkits. I honestly don't think you'll need it, but it's up to you. It won't hurt.
I don't think you need the metal protect which is really scale protect so long as you keep decent control over the pH in your spa. I think that between lowering the TA and adding 50 ppm Borates you'll be able to manage. You can always buy it later if you find your pH tends to be too high and you worry about scaling. The general rule is to minimize what you add to your spa to keep things simple, easier to manage, and more affordable.