1: Plastic ammo cans similar to the metal USGI cans, MTM brand I think.
2: Powder and primers are just stored in their original containers in a wooden cabinet - in an air conditioned room. Ditto with dies and all other reloading supplies. I used to keep them in the shop, but I had problems with rust.
3: I have metal desiccant packs that can be refreshed in the oven. There is a little window and when it turns pink it's time to refresh it.
Similar to this:
https://www.amazon.com/Dry-Packs-Sil.../dp/B006L882NM
