Take a deep breath, its just a pool.
You have all of the tools now and the support of TFP, now its up to you to figure out what to do next.
Choice A - Stick with TFP. Your costs will be limited to liquid chlorine, occasional jug of MA, and annual test kit refill. No real hidden costs other than that, but does require daily monitoring of your pool during the swim season.
Choice B - Go the pool store route. They handle the testing, tell you what you need, and you pay them. Simple enough and you can use your tabs and the other stuff you bought. The hidden cost will be buying stuff you don't need (you already rattled off $250+ worth of stuff they sold you that you shouldn't use) and the occasional draining of your pool (they will use terms like "chlorine lock" or "your water is old"). Hopefully we have at least educated you some to avoid these items.
The choice is yours. We all hope you go with Choice A, especially since you seem to be willing to do the work/research. I still think you are discounting the hidden costs of choice B, but its your pool and your choice.
The good news, regardless of what you choose, is that TFP will always be here for you, whether that is later today or a year from now. Good luck and keep us posted on how we can help.