I realize you are trying to help but honestly, buying an animal from a big box pet store just encourages them to continue buying and mistreating animals. I am glad that you took the time to take care of an obviously sick animal. That was very kind of youNext time if you are thinking about doing rescues, check if there is a local reptile rescue where you can adopt an animal in need of help.
All that aside, I think there are still a few things husbandry wise that you can do to make this snake even more comfortable. A 29g tank for a 35g ball python is not going to work. It is just way to large. Even if he is eating now, he could stop eating later and I bet you the big tank will have something to do with it. Ideally you should put him in a 6qt rubbermaid tub, but if you want to stick with tanks, a 10g would be better.
I don't know what you are using to heat, regulate temperature, or measure temperature but these are pretty important to know. Belly heat (with an under tank heater) is best for ball pythons. The catch with these is that they must be used with some kind of controlling device. A reptile thermostat would be best but a light dimmer or rheostat will also work in a pinch. Digital thermometers with probes or a temp gun are the best ways to get an accurate temperature reading. The accurite weather station from the home depot is a great little device for single setups.
Hides are also very very important. You should have two identical tight fitting hides for you little one. Half log hides will not cut it. They need the "rock cave" kind of hides that are low to the ground with a small opening.
You might have all this right already. I am just throwing this information out there because sometimes it can be very helpful to people who are new to ball pythons.
Good luck with that very tiny one!