Rescued SICK Betta From Petsmart, SOS!!!

Drogon, my newest rescue from the hands of the worst pet store, has been under the weather, so to speak, but I CAN’T FOR THE LIFE OF ME FIGURE OUT WHAT THE CAUSE IS. I couldn’t see any obvious symptoms on him, he just laid around the bottom of the tank, or on a plant. When he would swim around (short periods of time) he would jolt a couple times, then rest again at the bottom of his tank, which led me to think it may be ICH, because I’ve fought that pesky disease that fair share of times enough to know some of the signs that aren’t the obvious white dots on their body. However, those weren’t present so I couldn’t single-handedly confirm that’s what it is so course I had my water tested. It’s perfect no issues whatsoever. I’ve had a Betta who suffered from SBD, Popeye, and even dropsy. So, I’m familiar with specific signs of illness, and what to look for, but in this case, it’s hard to identify the underlining route to his sickness. When I went to my local aquatic store and showed pictures and explained the situation the associate convinced me (or at least try to anyways) that that was just his personality. He’s fine. I’m sorry, but I refuse to except that. After googling and staring at him for hours, I thought I may have seen ICH on his ventral fins and started treatment. I’ve treated the tank 3x now, and haven’t noticed any real improvement. So now I’m second guessing myself wondering if I’m completely wrong, and that’s where y’all come in. I desperately need help, determining what is ACTUALLY wrong with him. I don’t want to lose this sweet guy after rescuing him from what would have been his ultimate demise anyways…
Tank Size: 3.5 G
Tank Mates: random snails (had a mystery snail that kept popping babies out) with 2 different type of live plants.
Temp: normally 78, but I crunk the temp up to 80-82 (treated for ICH, remember?)
Tank does have a filter, and I have an air stone for extra support because of the increased temp.
Ive treated the tank for ICH, using ICH-X, 3x now and today will be the fourth (unless someone has any suggestions)
Carbon filter has been removed, and I’ve preformed 25% water changes with each treatment. I don’t know what else to do, PLEASE HELP A GIRL OUT!!! Check out the pics I’ll share, and see if maybe you can see something I’m oblivious to… let me know if there’s anything I left out. Thanks I hope we can save this baby

What are you using to test your water? That might be making the tests inaccurate

You say your water perameters had "no issues"....what were the water parameters exactly? Like the exact ammonia, nitrite, etc.

Did you cycle your tank before adding him or are you doing a fish-in cycle?

Definitely get that fake gravel out and switch it out for a more natural color. Black, tan, white gravel/sand are good colors.

The gravel/fake decor, is it fish safe?

Also, you said the tank is 3.5 gallon, but the tank water level is very low, so it's only about 2-2.5 gallons.

He is so pretty and he looks healthy to me, so it might be something in the environment.

Need pictures without the water marks on the glass.

Need a 1-2 minute video of the fish resting, moving, feeding (if possible).
You can upload videos to YouTube, then copy & paste the link here.
If you use a mobile phone to film the fish, hold the phone horizontally so the footage fills the entire screen and you don't get black bars on either side.

If the fish eating well?
How often do you feed him?
What do you feed him?

What does his poop look like?

What is the ammonia, nitrite, nitrate and pH of the aquarium water?

What symptoms does he have besides laying around all day?

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Keep treating for a few more days to make sure there are no external protozoan parasites on him. It doesn't look like there is but finish the course of treatment just in case. Then do big water changes and gravel cleans to remove the medication.

Don't add any more medication after that unless he develops a known disease.