I have tons of powdered milk left over from camping and I want to get rid of it all
If you make yogurt or kefir, you could use some of it in that. I don't know for sure, but I'd guess 50/50 fresh milk with reconstituted milk. Then mix some of the yogurt/kefir with feed and feed to your flock. Fermenting milk breaks down most of the lactose as chickens can't digest lactose.
Meal worms eat grain products not dairy products.
I've heard of folks (there is a poor website out there suggesting it) who have fed powdered milk to mealworms. Most people regretted it...I can't recall exactly but it wasn't good. My take on it is it is perhaps a technique used by expert worm breeders. Be careful with what you put in your mealworm bin, it can be hard to get it out if it doesn't turn out right. I only use wheat bran and carrots.