Would someone point me to the spot in the rules that mentions "Interrupts" are once-per-turn or once-per-trigger abilities?

Thanks!

~Andrew

Interrupts aren't once per turn, but they are limited to being executed once each time their triggering condition occurs. If the triggering condition occurs multiple times in a turn, then the interrupt can also be triggered multiple times that turn, with a limit of once each time the triggering condition occurs. The Interrupt section in the RRG glossary could be clearer to this point, but the second dot point covers it, specifically by using the term "another":

"The player with the initiative always has the first opportunity to use an ability that interrupts a given triggering condition, followed by his opponent, after which the player with the initiative may use another interrupt, and so forth."