Well some people fast their bettas so they can have a day or so to clean out their systems. I go home every weekend from my dorm, so mine are fasted from Friday afternoon to Monday morning, and they do fine. They've gone 2 weeks without food before when I was out for Spring Break, then I was sick the next week and stayed home. If you feed a lot during the week, I would recommend fasting, but if you feed lightly, then don't worry about it unless he starts getting bloated. If you feed your fish too much in one sitting, it can cause swim bladder disorder (SDB) it's not deadly or anything but it sure makes him swim strangely. Just keep in mind that a betta's stomach is the same size as his eyeball, and feed accordingly. He doesn't look bloated in your new photos to me! I think he looks fine and healthy. I have one of mine in a 2.5 gallon with no filter, and I change it twice a week, so it's fine. But every 2 days is fine as well! Whatever works for you! And congrats on your new little buddy, sorry for the novel I just wrote, and welcome to the forum!