How to treat stubborn Betta illness(es)?

I've had a Betta for a year now. Despite frequent water changes (every 3 days) and dechlorinated water, he developed fin rot while in a Marina Betta Pals 1/2 gallon tank. At that time I was also (fishless) cycling a 10 gallon for him. I treated him with Tetracycline and Jungle Fungus Eliminator as well as a small amount of salt in his 1/2 gallon. The fin rot appeared to stop but his fins never fully grew back. My initial fishless cycle stalled for 3 months and then my tank (which was bought second hand) sprung a leak. So I bought a brand new Waterhome kit. And started the fishless cycle again. I added my Betta to it when the cycle was complete (2 months later), along with an Apple snail. I kept it at 78F, the ph was 6.7. It included a piece of driftwood, silk plants, gravel, heater and an aqua clear filter. I had a power outage a couple of weeks later which destroyed my cycle. My Betta still had not full recovered from the initial fin rot (his fins still had not grown back 100%). I had to re-cycle my tank, and was advised on a forum to keep him in it. Rather than put him back in a 1/2 gallon. 2 months later he developed fin rot again and became lethargic and stopped eating. I isolated him in a 1 gallon bowl for a few days and began treating him with Tetracycline and Jungle Fungus Eliminator. Initially, his dorsal fins began to grow. I went out and bought a new 10 gallon kit to use as a hospital tank with a heater, filter, cave, silk plant and bubbler. I seeded it with gravel from my cycled tank and did water changes as needed to keep toxic levels at 0. The medication appeared to stress him and cause him to have a hard time breathing. Once the treatment was complete, I did a water change and he appeared better for a week. He was also eating again. I kept the water clean and added salt. A week and a half later he stopped eating. He also turned pale and started lying on his side at he bottom of the tank. The tips of his fins still had a bit of white on them. I started treating him with Triple Sulfa yesterday. I am using the medication suggested on the Betta Talk website. I didn't add the Jungle Fungus Eliminator this time because last time it seemed to be too much for him. I think he may have a bacterial infection. I don't know what to do anymore. I have spent so much money on this. But nothing seems to help. Sometimes I find him just floating vertically. If I touch him he darts away. How can I help him?