Tapping on glass shouldn't cause a regurge unless they were trying to scare the bajeezers out of the snake, and even then typically it would just ball up.

Snakes rarely regurge but it happens occasionally and when it does you should wait 2 weeks before feeding again so the snake can recoup the ability to digest properly again.

If your fuzzy rats are as big as mine then your feeding the appropriate size IMO
My 2 week old fuzzies generally weigh about 20-25 grams.