Uhh…math. First you’d have to have found all of those solutions in the first place. Each of them would have to come from a separate Public Persona. So that’s submitting for a MPID and then hashing it and reading it’s first three characters. You’d then have to resubmit to the network for a new MPID every time it’s not one of the ones you haven’t found yet. Then once you do find one, you have to start all over again for the next Public Persona. This is the exact same problem (but with an extra hash) as the current naming system is going.
Yes, but this is only for the Paper Napkin Test. I only have to remember the site name and the trailing three characters. That’s not so much to ask for - it’s not even one extra word! Also, if there are any other friends who know of that site, use the Petname System! You can submit the Nickname (domain name) to them and see if they have a matching Petname for that Nickname. If not, but they have a similar one, you may trust a group super majority that centers around one agreed-upon name.
Yes, but you’d only be able to do so with a new Public Persona every time. Once again…math. It’s prohibitively (statistically) hard.
EDIT: This thread should have most of the answers you’re looking for.