Formalin can be found in some of the commonly sold meds for fish like Quick Cure. It is a carcinogen though, so you want to take care while handling it. It can also be harsh on fish, but there are alternatives to this when it comes to chemical baths depending on the disease you are treating for. Acriflavin is one and can be found in Ruby Reef Rally as an example.
I wouldn't suggest a UV for QT, but might be useful in an Ick management situation. So you don't need to worry about that one or Ozone. Adding oxygen is as easy as what you already know.... pointing a powerhead at the water's surface.
The freshwater dip is one of the most important tools we have at our disposal. It's a great diagnostic, it can buy you time to get treatment set up and ready for the fish, and even is needed as a precursor to treatment -not just to buy time. It's easy, free and should be something you get very used to doing if you plan to add more fish to your tank.
Powerheads and heaters are pretty easy to come by and dont' need to be expensive for QT purposes. Used powerheads can be picked up on the cheap and stored for when/if you need them. I don't see a reason for you to need more than two max and that's if you want to have an extra on hand... or have one for each TTM tank. That's up to you. I dont see a reason to have more than two heaters as well.... again up to you.
It can be very overwhelming and your mind can run away with itself trying to get everything lined up. Any time you need clarification or just somebody to simplify points like this for you, post up. We got your back.