Yep, I feed off the chewers as well. I also don't offer anything for my rats to chew on other than their rodent block food. A block of wood won't stop them from chewing, chewers know that chewing=freedom. And they will teach others! I added some new blood and had to feed off almost all of them, plus some of my own stock.
As for fixing the tubs. I just solder/drill some little holes around the hole and wire hardwired cloth over the chewed hole.