Need advice betta with clear fins and considering moving him hack to his old tank

[bettalover123]

My betta has had fin rot for months and I'm starting to get very pissed at this disease. It's killing my betta and my bank account. I've tried countless treatments and now my betta refuses to eat and his fins are clear. I can't tell if this is a sign of healing or a sign of him not eating enough. My water parameters are .25 ammonia 1 ppm nitrite 40 nitrate. Yes they are a bit high due to a few doses of kanaplex. Should I move my betta back to his 5 gallon tank and out of the tank full of baby guppies which poop a ton and make my tank extremely dirty? Also why are my betta fins clear.