General Questions about Pesach

Question

Dear Rabbi, I have been following your list (and website) for years now and I understand the concept of relying on ingredients. However, I would like to know why we don't have to be concerned about the following: 1) Starch that may be chametz that is dusted onto paper plates and may get into our food. 2) Vessels used in the preparation of foods that may have been used in the manufacture of non-kosher or chametz products and not subsequently kashered/cleaned off. 3) Vitamins, additives, enzymes, etc. that have been added to foods and may be derived from grain. (When we eat the food, even if these are non-edibles, why isn't it a problem of achshvei?) 4) Would it make a difference if we actually knew what these derivatives are from, or if we actually knew what the machinery used in the factories was actually used for besides kosher food? Why or why not? 5) Some people buy products based on ingredients only before pesach, since then they can rely on bitul of residue of chametz that may have gotten into foods from improperly cleaned equipment. From your words I already know that this is unnecessary. I'd just like to know why. Thank you for your terrific work for Klal Yisrael.