Betta With Fin Rot And Parasite?

I got my rose tail betta in April and he was doing great at first. About a month ago, I noticed that he seemed to be having more issues with his tail with quite a few splits and some deterioration of the dorsal fin as well. It looked like fin rot and continued to worsen, so I treated it with Furan 2 which temporarily improved his fins. Now his fins are looking even worse than the first time, so I started the Furan 2 treatment again. Currently on day 3 of treatment and noticed this weird looking white ball between his ventral fins and I'm worried that it's a weird parasite that I can't find any information on (in pictures attached, water looks yellow from the Furan 2 treatment). I'm also worried about needing to treat him for fin rot all the time since he is a tail biter. I have a very low flow filter too since he struggles with pretty much any flow. He's in a 5 gallon, heated to 81 degrees, and pretty heavily planted so he has lots of places to rest. Water parameters are GH 60, KH 80, PH 7.2, 0 nitrite, and 10 ppm nitrate. There are 2 amano shrimp and a mystery snail in the tank with him since he is very peaceful and they don't bother each other. The tank was cycled for a month before I put any of them in. I do 25 to 50% water changes weekly, but I have been doing them as directed for Furan 2 treatment. I feed him daily with a variety of freeze dried blood worms, brine shrimp, and betta flakes and I fast him one day every week or two. Any advice on what this weird white thing is and how to keep his fins un-shredded?

 

First, gorgeous betta! Love it! I see what you mean in the first photo. I've never seen that before. Could it be a mystery snail egg?
I don't think you should treat fin rot constantly because of tail-biting. That can harm your fish and other critters going through treatment all the time, plus make the bacteria resistant to meds.
The best way to prevent bad bacteria such as what causes fin rot is to keep the water and tank clean. Seems like you're doing that (although you didn't say what the ammonia level is?). Maybe you'll need to water change biweekly?
Does his tail get worse or does it stay the same?

 

ammonia is 0! his tail has been getting worse and there's nothing in the tank that should be ripping the fins, but the tail looks more split right now than it does look like fin rot. The dorsal fin does have some fin rot (looks like the edges of the fin are flaking off almost), but not horrible. Its hard to get good pictures of him since his coloration is so dark. He also has some red streaks showing up on the dorsal fin and spreading of the red on the analfin, but I'm thinking its just a color change since he's always had some red. I'm just not sure how to keep his tail from splitting since the filter is already at such a low setting and there's nothing that should be tearing it in the tank

 

my mystery snail has never laid eggs that I know of and it seems pretty stuck on him. He still seems happy and is making bubble nests, so he seems okay other than the shredded looking fins and the weird ball

 

If he bites his tail, there's nothing you can really do to stop him. He may do it from stress, bad conditions, boredom, or just a thing he does. There doesn't seem to be anything that would cause him stress and conditions are good, it might be one of the latter two.

I have no idea that ball thing is. It's pretty big.

 

It fell off of him. As long as it's nothing to be concerned about I guess it's okay, but it's still really weird. It looked almost like a calcified ball of something.