Help with Betta and tank

About 8 months i purchased a betta from a chain pet store for my girlfriend for a present. Before i bought it i obtained one of the 5 gallon hex tank kits. It was a fish less cycle that ran for a month. I could never get the ammonia below .25 on the test kit but the nitrate was climbing and the nitrite was not there so i thought the test kit had expired since it was a few years old. The betta was introduced with no problems and weekly water changes were performed. Then about 3 weeks ago was midterms for our college and i neglected two water changes. One morning she noticed that the betta had developed pop eye. That night i did a water change seeing no abrasions to him so i figured it was a water quality issue. The next day i also performed a water change and this seemed to put him on the mend. i tested the water again and the ammonia was at .25 again and the nitrate was high at about 100, which i figured was due to the two weeks missed. The nitrite was 0 but the curious thing was the pH. It was down to 6.5 when the tap water reads 7.5. i thought this might be due to the ramshornn snails that i introduced to help control the algae problems the tank had been having. I thought that the snails might be taking the hardness out of the water and taking away the buffer. This is when i adopted a three day a week water change and this did seem to help. Also, he was reduced to a once a day feeding and i obtained a sponge filter that i placed in the tank with an air pump. Then yesterday life again intervened and i missed one. his eye became worse again. I did a water change today and i tested the water again. The ammonia held steady at 0.25 and the nitrite was 0 and the nitrate was 10, this was after i had obtained a new test kit. This time the pH had dropped to 6.0. This has me concerned and i did not know if this was something more serious than water quality and if perhaps i should take a new approach. The temperature has been steadily between 78 and 80 degrees sense he was obtained. Any ideas are appreciated.
I know the pictures are not the best but i only have a phone and if better ones are needed than i can try to obtain a proper camera.

Thank you for the advice. The tap water does have ammonia and this tests between .25 and .5. I thought that this would have been converted by the filter though so does it just add to the nitrogen load of the tank? Yes I use prime every time I change the water though I dose about 5 times the amount, it says the first ring is for 5 gallons and i just do half the cap because i heard that you can dose up to 10 times while being safe. I change roughly 60% of the water volume with each water change. There are probably 50 to 60 snails in the tank. I will feed once a day and i am going to start doing the twice a day water changes. Today i went to my lfs to pick up an assassin snail just trying to control the snail population just for aesthetics. While there one of the workers told me that the water changes could be too frequent and suggested once every other day at most. This struck me as odd and i plan on disregarding this. The person also sold me some medicine called Betta Revive, i bought this because it was only 2 dollars but it got me wondering if i should use it at all as i don't really like using medicine. Also, the person telling me about the water changes made me a little weary. How long should i wait to see if there is any improvement before i treat with some medication and should i use what i bought or should i go ahead and buy the Maracyn?
Thanks for all of your help!

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Thanks for the suggestions.

Thanks for the suggestions. The tap water dose have ammonia and it tests between .25 and .5. I thought that the tank could filter this so does it just add to the bio load of the tank and if so is there anything that i can do about it? Every time i change the water i use prime though i dose a little high because i just dose half the cap which it says is for 25 gallons though i heard that you can safely dose 10 times over so should i change anything? I change 60% of the water volume each time. There are probably 50-60 snails in the tank and today i went to my lfs and obtained an assassin snail to help out with the snails for aesthetic reasons. When i was there i asked one of the workers and they said that I was doing too many water changes and to do one very other day at most. I plan on ignoring this, but she also sold me some Betta Revive for 2 dollars so I bought it. Should i use this at all? And how long should I continue the water changes and wait for the results before resorting to medication which i am hesitant to do?

Thank you so much for all of the help!

The betta is doing better so far. The one eye is down a good bit and the other eye is down moderately but it was never nearly as bad. I am going to start manually removing the snails that I can. I really don't want to use the medication but if he does get any worse than I will set up a small treatment tank for him. Thank you so much for all of your help!

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