Does my boy have dropsy?

I just noticed most of the signs today so I haven’t done too much treatment but from my limited knowledge of dropsy the prognosis isn’t good so I wanted to ask for advice immediately. I’d really appreciate anything you guys can offer me here. Let me know if I’m doing anything wrong, I’ll do whatever I can to save him. I tried to get some pictures but my camera isn’t great so lmk if they need to be clearer.

Housing:
How many gallons is your tank? 2.5 (I know it’s not ideal, I feel really bad)
Does it have a filter? Yes
Does it have a heater? Yes
What temperature is your tank? 80 degrees
Does your tank have an air stone or other type of aeration? No
Does your Betta have tank mates? What kind? No

Food:
What food brand do you use? Aqueon, occasionally bug bites, frozen daphnia, brine shrimp, and mysis shrimp to vary his diet
Do you feed flakes or pellets? Pellets
Freeze-dried? See above
How often do you feed your Betta? How much? 5-6 pellets per day

Maintenance:
Before your Betta became ill how often did you perform a water change? Once per week
What percentage of water did you change? 75%
What is the source of your water? Conditioned tap
Do you vacuum the substrate or just dip out water? Vacuum
What additives do you use other than conditioner? What brand of conditioner? API Stress Coat+

Water Parameters:
What are your water parameters? Please give exact numbers. If tested by pet store please get exact numbers. "Fine" or "Safe" won't help us help you. Important: Test your water before the regular water change; not after one.

Ammonia:
Nitrite: 0 ppm
Nitrate: 10 ppm
pH: 7.8
Hardness (GH): 200? (couldn’t get the exact number)
Alkalinity (KH): 150

Symptoms and Treatment:
When did you first notice the symptoms? He’s been lethargic for a few days but I didn’t think much of it because he’s never been very active. I noticed minimal bloating a few days ago, and pineconing today.
How has your Betta’s appearance changed? Pineconing and bloated
How has your Betta’s behavior changed? Lethargic and trouble swimming
Is your Betta still eating? Yes, he’s still hungry and goes to the top of the tank whenever I come by in hopes of food.
Have you started treating your Betta? If so, how? I just moved him to a 1 gal hospital tank with aquarium salt. Picked up both Bettafix and API Melafix from the store today, but I haven’t used them yet because I wasn’t sure which would be better. Any thoughts?
Does your Betta have any history of being ill? He was finbiting when I first got him and although they’ve partially grown back, they haven’t fully recovered. My thought was that might make him more susceptible to infection, leading to dropsy.
How long have you owned your Betta? Around 9 months
Was he or she ill or suffering some sort of damage when purchased? Not to my knowledge

In the last photo he’s hiding behind the heater at a 90 degree angle. My poor little guy…