There isn't a "hub" per se, but it is a rather strong community. Most affiliates operate through the larger affiliate networks as a central location of advertisers, publishers, and tracking.

In most affiliate marketing programs the advertiser doesn't report the conversions - tracking and payment is handled by the affiliate network as an intermediary, which has it's own pros and cons. But they will fight for affiliates when commissions are due.

DM me if you'd like to talk more about that, I work in the industry.

Well, you can still track number of clicks by yourself to get a ballpark figure. You'll just have to believe the conversion number they tell you, but should be able to estimate whether it's realistic or total nonsense based on conversion rate.