1. One gallon tanks is not that big, you can surely get one pretty Cheap. You can even get one of those plastic critter keeper to put him in, get one that is at least 1 gallon. They are onyl a few dollars.
2. Yes, a dechlorinator is needed. But if you do not have one right now, you can age the water too. Put tap water in a bottle, keep the bottle uncapped, let it stand for 2-3 days, then take some water out of his tank and pour that aged water in. Change it every 2-3 days if your tank is 1 gallon.