I would also do something to make sure they can't open those drawers. Looking at it without a size comparison, it is hard to get an idea of how big the drawers really are. Housing 4 rats in each drawer constantly seems a bit too much. If you will be housing the male in with the females 24/7 then I personally would not put more than 2 females and 1 male in there. When you get litters and the babies start moving/hopping around, that space quickly fills up.

As for food, I read somewhere that rats eat 15g of food a day, each. I do not measure my food out. I just scoop some out of the bag and put it in the tub/tank. When I notice it is getting low, I add more.