You will need to cycle the tank. So you will need liquid test kits for not only PH, but Ammonia, Nitrite, and Nitrate. API test kits are good.
I keep the substrate clean by siphoning it with a long length of small airline tubing. You want a small diameter to give you enough time to get everything on the bottom.
Do not use distilled water.It is devoid of certain elements the fish needs. Use tap water that you treat with Prime to dechlorinate{or some water is treated with chloramines, this will elminate that also}
No, when doing a water change, after the tank has cycled, you remove approximately 50% of the water while cleaning it, and replace with dechlorinated water.
Feed once a day,sometimes twice is ok but keep the amount tiny. Give a day off occasionally. Sometimes after the day off, defrost a frozen pea or two, take the skin off cut in half and feed. To keep the digestion moving.
Purchase some good quality Indian almond leaves and add a small piece to the tank. This helps ward off fungus, and helps with overall health.