Good question.
1. Blowater's relay list can be modified and sync across device.
2. It uses a CRDT approach which you watched last week. It is not compatible with NIP-65 and is more stable than NIP-65, meaning other client can't mess it up. I will draft a NIP to let more client adapt it.
3. Yes, Blowater should somehow discover a npub's relays in a "smart" way, be it NIP-65 or other methods. Then the user can choose to copy these discovered relays to Bw's relay list.
NIP-65 is a little more than just relay list syncing, it includes the inbox / outbox model (I think everyone calls it the gossip model) https://github.com/nostr-protocol/nips/blob/master/65.md#motivation
To summarize, the idea would be to send the DM events to the other users "read" relays so that you can be certain they will see the event.
The CRDT approach your using probably works better for relay list syncing, but I don't think It would work for the above scenario since the events are encrypted and other users could not read them. and therefor would not know what relays to send the DM events to.
All that said, send me a DM or let me know when you have something written up about the CRDT approach. I'm really interested in learning how it works
