Advice on sick Betta. Possible Dropsy?

About a week ago I noticed my betta, Florence, had a lump on his right side. In the days prior he was very slim and active. On the day of finding it I noticed he was still normal, his appetite hadn’t changed, he was swimming actively and his normal responsive self. A couple days passed and the lump became larger. I then noticed his tank had white flakes all over so I decided to clean his tank fully.

As I cleaned his tank I found that these white flakes were paint chips coming from the small cup I had re-purposed, the paint was randomly now chipping. So I threw it away.

After putting him in his tank I began researching what the lump could be and initially I thought it was swim bladder disease—right before finding the lump I had been feeding him a bit more than usual. His normal diet was 2 balls in the morning and 2 balls at night and the occasional fasting. But as he began showing more interest in playing with me I would give an extra pellet or two as a reward for his efforts.

It has been 3 days since then and his bump went down and rose once again, now bigger than before making the scales stand on his sides a little. He now has a harder time swimmimg, keeping his balance, and when he gets to the top of the water to get some air he swims, then floats right to the bottom even while still trying to swim. After getting to the bottom or using the cot I made to keep him closer to the top he leans to his right, sometimes left, and lays there looking exhausted. Both sides are bloated but the lump is more prominent on his right. He still wants to eat but I tried the 2 day fast then giving him some pea. It takes him a minute to get it but he eats.

So today I got a new tank (his original was 2.5g) this new tank is 10g. New rocks, new filter, air stone/pump. I also decided since there hadn’t been change with the fasting and pea, I would do a epsom salt bath. I did 1/4 tbsp:1/4 gallon of water, and a 1/4 tsp:1/4 gallon of water as a recovery bath. In the 1/4 tbsp salt bath he passed out a little, swam but wouldn’t move so I slightly pushed him up, he got air and repeated, so I took him out after 45 seconds and put him in the recovery bath, he swam more easily but still wouldn’t move and laid there slightly gasping, so I would touch him with the net and he would wiggle his fins letting me know he was okay. After 15-20 minutes I took him out and put him in a half gallon of fresh water with a little of his tank water and some drops of Tetra Aqua Safe water conditioner. He’s been in there since, I decided not to put him in the old tank and put him in his new tank but its still filtering. But he is looking more active, the swelling and lump look about the same, it did go down for a few minutes but looks the same again. He doesn’t look so in shock anymore so I was thinking to give another bath tomorrow.

He’s now in the container he came in with the water he’s been in, inside of the new tank acclamating to the warmth (79°F) this made him more active in the last couple hours but he still isn’t his normal self. I plan on putting him in his tank tomorrow.

I can’t decide if its dropsy because his scales aren’t standing up, but they kind of are where he’s at his widest. Then again he’s hungry so I don’t think it could be swim bladder disease, but he hasn’t pooped since being quarantined and having some pea. I don’t know what to feed him, I don’t want him to starve but I don’t want to potentially make him worse.

EXTRA INFO:

-I have had him for almost a year

-I have been lazy with cleaning a lot of the time. This last time it had been over a month since his last cleaning, but it wasn’t the longest the tank had gone without a change, sadly.

-The filter wasn’t used a lot because it created too much force into the tank and he had a hard time swimmimg.

-Prior to sickness I did start using the filter more.

-His heater ranges from 75-79, I can’t set it, its automatic to the water.

-Practically his whole time being here has been spent in the kitchen area, in the beginning on a counter away from the stove and cooking area, and later beside the stove (about 4 1/2 months as we moved to a new place) his new tank will be out of the kitchen entirely.

-His last poop was a huge clump on Sunday 7/26/20

-His food is Tetra BettaMin small pellets