I've already found the answer to "After offering food to a kuman thong and leaving it with him for some time, should the food be disposed of or can it be ingested by a human being?"

The answer is yes, it can be ingested by a human being. There is an incantation that is recited before taking food offerings away from the kuman thong. After the incantation, the food becomes normal food once again and is no longer spirit-offering food.

I am referring, of course, to wrapped candies and fruit. Exposed food, milk, water, and soda in tiny vessels should be disposed of, liquids always at the kitchen sink.