Yeah, they didn't get rid of the old food items, but you can still use them to craft. If you hover over an item, it'll say what it can be used in place of. Correct on the vault slots, only usable once.
I'm a bit fuzzy on the clan thing, but you needed 10 people to form the clan. Once it became "established", which was tied to a certain amount of activity IIRC, then you didn't need the 10 people to stay. If nothing else, you can always use the mail system to transfer items between characters.