Hi,

I'd definitely remove the rat if the snake isn't interested.

Keep it till next week if you want or kill it and freeze it if you don't. Do not release it into the wild - that is probably illegal and unfair if it isn't.

I'd stop all handling at the moment and leave the snake completely alone ( aside from cage maintenance ) for a week to settle in to the new surroundings. At his size a few skipped meals shouldn't do him any harm but a picture to judge his body condition could help us be sure.

Did you ask how the previous owner fed him? Sometimes the steps beforehand can be important too.

And to the forum.