I do not work with structural entomological pests; consequently, the only information I have available is from fact sheets generated by other nearby states. It sounds from your message and question that you have already found some of this information on your own.

Another suggestion you could follow and maybe you already have follows:

Dispose of chocolates, grains, pasta, hard pet food, etc. that could be infested with eggs or immature larvae. Cleaning the shelving and storage area would be next. It sounds like you've done these two parts multiple times... Purchase plastic containers to store newly purchased grains, food items, etc... (food that was infested and removed). Keep those containers closed until that food item is needed. This should remove the access to food the caterpillars/pest needs for development. I would continue to do this in order to ensure remaining eggs that hatch have no source of food.

Have you seen the caterpillars in your food? There is another moth that looks similar to the Indian meal moth (grain moth) and they infest similar foods. Sometimes I think clothes moths can also be confused as the grain or meal moth.

As you mention, there are no real viable pesticides available for treating this pest - especially since we do not want to put pesticides on our food. One method of killing the insects in the food is to freeze it for 24-48 hours. The dead insects could then be sifted/filtered out of the food and that food could be eaten. The insect does not really make the food inedible, but many people do not like the idea of eating insects or parts of insects (they are really just healthy protein). If the concern is eggs that haven't hatched then you could freeze the food longer (we eat many insect eggs in or on vegetables, fruits, pizza sauce and it isn't a concern).

I think the best preventative option is to place purchased food stuffs in plasticware to protect it from infestation. As the insect pest starves (when eggs hatch and no food), the problem should end (no food, no pest).