communick.news fits all you requirements regarding users - only paying members can join, so the instance is pretty much guaranteed to be protected from spammers and bots.

Regarding your communities: I really rather keep a strict separation between “instances for communities” and “instances for groups”. The topic-specific instances I am running are meant for specific niches, but perhaps I can find one domain that can be used for more “generic” subjects. Would you be interested in that?