That IS strange. I seem to average about 6 wheaties per box. And a box is $25, so 2,500 pennies. With five TIMES that amount through your machine, you should have about 30 wheat pennies. Or MORE, since my area seems to have lower amounts of copper overall than otehr areas. I'm running around 16% copper. Other areas are running as high as 22% copper, so I would think they get more wheats too. But, NO wheats? And you are showing about 24% copper if your numbers are accurate!
Are the coins from the Fed, or from a local bank? Maybe you are getting coins that hvae already been searched for Wheats. Not for copper, but for wheats. that is a good possibility. make sure you are getting full boxes, and that they are coming form teh fed. They should be rolled in plastic wrappers or white ones.
I bought a bag of 4100 of pennies and found zero wheats. I thin ksomeone went through them. Not necasarily the bank, but maybe whoever turned them in. Either way, I make sure i get Fed boxes now. I've had ten wheats in a box or two, and only once a box of 2, but I seem to get about 6 - 7 pretty frequently.
I'd change out my 1981 penny that is in the machine. Go to a new penny in there. (It won't make a bit of difference, but then if you get nothing, nothing has changed, and if you start to see a wheat or two then you'll think it changed your luck. LOL)