Yay!
It's always a good feeling when one who's been off food finally eats again. 515 grams is a decent weight. It's hard to give static numbers because different snakes eat and grow at different rates.
You could try him on rats, if you can get them easily for him. In general we try to get our snakes eating rats. Not necessarily for better nutrition as some think, but simply because rats get bigger than mice and in general it's easier to feed one decent size prey item as compared to 3 or 4 small items.
The temps seem a tiny bit on the low side. Not huge, maybe 3 degrees off ?
I'm not sure about a humidifier, you have to be very careful about anything you put in the tank, because I've seen some real horror stories where a ball got stuck inside a pump or waterfall placed in the tank and had to be cut free. Scary stuff. Unless your humidity falls down to like 20% I wouldn't worry too much about it. Simply providing a humid hide for him to use as he needs it should be fine. Humid hides are simply a slightly larger hide stuffed with clean damp sphagnum moss and placed in the tank. When he needs the extra humidity, he'll burrow into the damp moss.
Gale