> Does it make use of all my published relay lists (inbound/outbound/search/DM/etc), or just some?

When you post, I am broadcasting to yours outboxes relays, if you are tagging someone, I will also broadcast their inbox relays. search relay is used when you search something, you can select other search relay in the search settings, now days is mostly nostr.band. the client will look for your inbox relays for your notifications and replies/reactions of your notes, the client doesn't have DMs therefor doesn't use DM relays for anything.

1. The relay lists in the /relays page under "Active Relays" are relays that were found as you navigate the app, in your home feed, the client will look for outbox relays from the people you follow and fetch notes from these relays, if you follow like a thousand people, it will find and connect lots of relays, the client cap the max number of relays per person (you can change in the settings) to make the number of connections more manageable, you might have concerns of too many websocket connections and a privacy implication, and you will be right, but this is the nostr solution relay centralization. The list of your outbox and inbox relays should be under "outbox relays" and "inbox relays" respectively, not under "active relays".

2. Follows or relays lists being nuke is common in nostr and supper annoying, specially for non technical users, please find and report which client nuked your list, I haven't heard of it in my client as I always fetch your list before publishing a new one, if you are logged with a browser extension make sure to check the event in the popup before signin the event, a follow event should have a bunch of p tags.

3. This happens when the client couldn't find the user metadata or still trying to find, it's trying to find the user outbox relays and fetch user metadata, sometimes this information simply can't be found as the user didn't setup their relays properly, changing outbox relays without migration result in things like this, this has nothing to do with search relays or your relay settings, mostly the user issue or a client issue, nothing really you can do.

4. Thanks for reporting that, haven't heard of this issue, , gonna try to reproduce it, yeah, cleaning the db likely won't fix the issue.

Keep reporting.