I agree that I think your being to hard on yourself. It's not all fault on you, Could you of researched a little more before you got him, sure but why would you when the pet shop leads you to believe that theres nothing to it? I wish pet shops had a little more care for their animals, had more knowledgeable employees and informed new pet owners of exactly what the animals require to be healthy but unfortunately most just care about making the sale.
The thing is, you have him now and your doing the right thing by researching and learning so you can provide the care that he needs. It seems complicated at first but it really isn't. 5 hours is a lot of handling for any animal lol, so don't think the ball python was a bad choice just because of that. They are actually a lot more tolerable of being handled than many reptiles and they are rarely aggressive which is why they are sold in pet stores so often, hard to sell an aggressive snake.
You will be fine. Just get your temperature and humidity right and then you can move on to researching how to get him to eat. After that, you will feel a lot better and start to be able to enjoy your new pet instead of stressing about it. I think your heart is in the right place and that is most important imo.