Glowy didn't make it.
After I posted this, we went out to Petland and the guy gave us some BettaFix. We ran home, put it in his tank but we were too late. Within a few hours, he was gone.
We are getting another one, but now I know what I really need to do. The guy at Petland told me that the betta kit I bought had absolutely everthing I needed, didn't say a word about a heater or pellets. I feel so terrible for just taking his word for it and not doing my own research, but he seemed so knowledgeable. Now I feel like I need to question everything he told me.
So, in a 3 gallon tank, I'll need a 25watt heater, a thermometor and I need to get some better food. 100% change once a week, rinsing everything and then filling with room temperature water.
Do I need to let the water heat up to the normal temp before putting him back in?
The guy sold me a moss ball to help keep the tank clean during the week between water changes. Is this helpful, or could it be harmful?
Is there any benefit to using the water conditioner that he sold me?
Thank you for your responses. I know I sound like an idiot and irresponsible fish owner. I feel terrible and I really want to learn the right way to care for the new one.