pH: 6.8
Ammonia: 0.25
Nitrate: don’t know
Nitrite: don’t know
Temp: 78
Any ammonia reading is bad. Try changing his water daily to make sure you get a reading of 0 ppm. I know the others here said not to change 100% daily, but if you're getting an ammonia reading, it's probably a good idea. From a thread I put up recently, the consensus seemed to be that having detectable ammonia was worse than changing water. The other posters might have assumed you had him in a larger container too.
Also, how do you know the temp is 78? Is that the temp of your apartment? Do you have an actual thermometer in the water that says 78? If not, try getting a water thermometer to make sure the water itself is actually 78 deg.
I live in New York and my LFS doesn’t have Esha 2000 or intrepet. They have BettaFix, Melafix and PimaFix. Are they good enough?
I doubt those are good enough for a serious infection like yours has. Hikari makes this thing called Betta Revive that is formulated in a size geared towards bettas kept in bowls. Betta Revive has both antibiotics and antifungal treatments in it. The manufacturer recommend dosing as per instructions and changing water daily. You want to keep your betta's water as clean as possible while you're treating him. There's always eBay, Big Al's online, petco.com, and amazon.com to buy stuff online from if your LFS doesn't have these things. And buy a few extra so you are prepared for the next couple of times.
Just beware, though--Betta Revive is a deep blue color from the antifungal methylene blue in it and it STAINS just about everything it touches. I was using it on my betta until I realized that the red spots on his head and eyes were pigment, not sores. I made the mistake of splashing water with the Betta Revive in it on my white wall and it left little blue spots that washing and scrubbing can't remove. The Betta Revive also permanently stained my sandstone rock that was in the 2.5 gallon container with my betta.
People here will be tsk tsking you for having your betta in too small of a container without a heater or filter, btw. A few rare bettas can live seemingly happily for years in bowls without heaters or filters. Given that yours is seriously ill, I'm guessing your betta isn't one of them. If you really want your guy to live a quality life and not get sick often, you should get him a larger home with a proper filter and heater. And a few plants.