Keychat is a standalone chat app. If a user adds their Keychat link to their Nostr microblog profile, it can partially serve the role of Nostr DMs.

For issues 1 and 2, since both sides of the conversation are using Keychat, those are basically solved.

For issues 3, 5, and 6, Keychat solves them completely.

For issue 4, if the user only uses relays that charge stamps, that’s also solved.