I don’t understand all of your questions, but I attempted to answer the ones I was at least 60% sure I understood.
It’s also stored on other nodes that request your content.
If you pass in multiple files into ipfs add they get wrapped into a single directory by default.
You can remove files from nodes you control, you can use ipfs pin rm to make sure the content isn’t pinned and then ipfs gc to garbage collect it. You can’t make other nodes remove files just like other nodes can’t make yours remove files.
ipfs-cluster will do this. It will let you pin (or unpin) content across multiple nodes that are part of the same cluster.