Actually, lack of appetite is not generally internal parasites. Fish with an internal parasite infection tend to be overactive and ravenously hungry, and despite eating well they lose weight. However, a lot of bettas with internal parasites infections will get secondary bacterial infections and that can cause lack of appetite. In this case he's probably not ill but stressed and maybe a picky eater.
How did you acclimate your new guy to his new bowl?
I would actually cut down a little on the water changes.. 3 water changes a week 50, 50 100 would be fine in that size, but I really would try to get him in something more like 2.5g + as it's really hard to keep bettas healthy in anything smaller, long term.
Your tank is at 76 but not heated? Are you using an in the tank thermometer to determine this? How are you keeping it this warm? Bettas should be kept on interior walls away from vents, cold air returns, exterior doors and windows. These things cause temperature swings that are very hard on fish. Their bowl temps will be about 4 degrees so or so below room temp. So if your house is at 80 then his bowl might be 76.
I would look for a different pellet and see if he will eat it. Try New Life Spectrum Betta. It has garlic and my guys seem to go for them the best. You can feed 5-8 split up into 2 or even 3 small meals a day. If you can't find those you might try Omega One Betta Buffet - feed 3-4 split up into two meals. One fast day of no food is necessary no matter what you feed.. obviously not your problem right now.
This is how you do large water changes without causing stress and/or shock to your betta.
To do a water change, use a little cup like a plastic solo cup - this cup must be only for him and have never been used with soap or other chems. Scoop him up in this cup (keep him in the cup about 1/4 full of water - it doesn't need to be much because he won't be in it for long) and leave him in the cup while you change his water. To do the 50% use a turkey baster - dedicated only to him that has never seen soap or chems - and drag it through the gravel and try to suck as much of the poop out as possible, in addition to 50% of the water. Use a thermometer under the running tap to get it to be the same temp as the water that is normally in his tank. When the thermometer says the flowing tap is the right temp, fill back up his tank. At this point, add the conditioner (dose for how much water you change - if you change half the water you add half gallon worth of conditioner, If you do a 100% water change dose for the full gallon change). Float his plastic cup with him in it in the new water. Slowly add a couple tablespoons of the new water into his cup every 10 minutes for at least an hour. Finally, dump him in gently but try to get as little of the old cup water back into the tank as possible. When you do the weekly 100% you will do mostly the same thing except empty his tank fully and rinse everything in it very well under warm water but never use soaps or chemicals. Once it's fully cleaned/rinsed you can refill it and repeat the cup/acclimate phase.