Are you going after people or machines as your target? It matters which, because machines can't do human trust, so then the issue of how you exchange keys and

Are you going after people or machines as your target? It matters which, because machines can't do human trust, so then the issue of how you exchange keys and establish trust is forced. What's the stop a MITM between a client and any other client from intercepting the conversation? In your protocol, nothing, except that if the MITM isn't there at the start, they can't join in right away. This is not a very useful assurance. So please, keep working on it, but I think your challenges are pretty serious. If the problems are fixable, then go ahead and fix them. I'd be happy to take another look - after that.