Flame Gourami consistently tilted

[ccc24]

I have a gourami that is consistently lethargic and sits at a continual angle. His gills seem like they might be a tad dark (I'm not sure what they should look like as this is our first gourami). 

He has a good appetite (he will perk up, swim straight and eat/chase down his pellets or live BBS during feeding time and then immediately returns to this state). He is currently in a 2-gallon hospital tank, alone, with heater at 78 and a sponge filter for minimal flow/aeration. I am treating him with 1:1 NACL and kanaplex (2nd dose today). 

With how thin he is, I am leaning towards a parasite and considering a dose of para-cleanse. Any ideas on how to dose a packet meant for 10 gallons down for two? I am leaning towards reconstituting it in 100 mL of dechlorinated water and utilizing 20 mL of the mixture in his next water change. 

Parameters:

• pH: 7.6
• Nitrates 0 
• Hardness 120-180 (hard to decipher exactly on the test strips but I have just short of liquid rock for tap water)
• Nitrite 0
• Ammonia 0
• KH/Buffer 80
• Water Temperature 78

[Colu]

If he's eating ok and still losing weight he could be suffering from wasting disease and I would recommend treating with fritz Expel p active ingredient is levamisole once a week for 3 weeks or you could add it to his food feeding the medicated food for 7 days 

[ccc24]

He has survived the night after his first dose of expel-p. Any ideas on what food might be the most dense nutrient wise, so whatever bites he gets pack the most punch?  He still has an appetite but he is incredibly lethargic. 

[Colu]

A good quality pellet or flake and a combination and of live or frozen brine shrimp Daphnia bloodworms vinegar eels will help build him back up