How many developers are there? Is it a one-man team?
It has virtually no marketing...
And how many users are actually using the app?
Is anyone able to answer my questions?
I think not. the dev (team) wants to remain fully anonymous, so how many there are isn't public information, you can always try asking (he doesn't respond on this forum, only through mail / twitter)
As for how many users.. It's still a wallet, maybe there's a way to find online nodes