Hey!
I wouldn't worry to much, especially if it has been eating pinkies. Keep working on the husbandry, it makes all the difference in your snakes behavior and health :)
And for a baby ball python I would recommend keeping it in the size tank you have now....They really like the clutter, makes them feel more secure and hidden from predators. (more difficult to clean though haha)
Also, can't really tell, but it looks like you only have a analog thermometer. If so, get a digital. Those analogs thermos are horrible and rarely accurate. And yeah, definitely get the thermostat stat! Hahaha.....Your substrate will get up to 105 degrees at 1" depth from the UTH. So if your snake hates the cold side hide, it will endure the heat anyway for security. I figured this out as soon as I got my infrared temp gun. Went and bought a thermostat immediately.
Let us know what happens though :)