re 3) 10k sats Not terrible- at the current sats/USD, it's similar to price of buying a domain for a year, which might be enough of a deterrent.
I wonder if maybe it could be something the community votes on for approval to avoid the potential spamming. Haven't been on indiehackers for a while but I think their subforum/groups functionality, after you apply and you need a certain number of people to express interest in joining before it becomes a real group.