Personally,,, I don't put that much thought into feeding my snakes, especially Balls. The only concern I have with feeding is getting them used to F/T meals over live, sooner or later they will take a feeding break, specifically males... With a snake that size I would have to agree with the weaned rats as an ideal size for him, at least once a week. You can't go wrong with once a week... And if he wants more, give it to him, "listen to him" if he is moving he still hungry....
As for the spurs,,, you are 100% the only way to be sure is probing. Good luck and have fun with him...