Not OT. I wish I didn't have to either. I know many at FB read HN, and I don't want to make a bad situation even worse by getting singled out for blowing the whistle on this clearly unfair (and possibly illegal) situation.
It just sucks to be in the position you are with essentially no leverage in the relationship, and dependence on a single source of advertising. I think the other comments offer some insights on how to try to diversify. I don't think you have a real alternative beyond that.
Good luck!
Would it still be legal if there was evidence that they had deals with Zoosk and Match.com to keep smaller advertisers off their platform?