You've got many issues that are confusing you. First of all, you feel bad but your test levels are good. If I were you, I'd look at issues other than your test levels - 545 is good. You can raise them with exercise and cutting soy, green tea, etcetera, but 545 is good.
If you try to find out why you feel like crap with good test numbers, then TRT is not an issue and you can stop obsessing about it.
Three shots is by no means too late to stop. You may need to run PCT, but it is not too late. The reason why TRT is considered for life is because people usually go on it once they have exhausted other possibilities. If you're hypothyroid, you can fix that without TRT - it's a last option, hence for life.
That being said, three weeks of TRT is too early to feel significantly better. I didn't really notice any bump until five to six weeks, and continued to have improvement probably for the first year.
I know some of the obstacles to narrow down your issues are problematic, but if it keeps you off TRT it's worth it. Follow KSMan's advice and you may discover you just need to use salt to feel better. If nothing works, and you do end up on TRT, you haven't lost anything. And, after 15 months on it, I feel pretty fucking good...but my test levels are only 650 on it, so I don't think that's your issue.