As long as the multiple servers run simultaneously I don't think this would be a problem. However, unless you're renting each additional server from a host, each server is going to suffer with exponentially worse quality every time someone joins a different server.
Then I'd say no. Its running from the same IP, so it is considered the same server. However, this is a mod's decision to make.
You can run multiple servers simulaneously as long as you give a different port for each. I guess it's not considered the same as long as the port is different.
That's not what is being asked. He's talking about threads in the forum. And the exponential worsening is referring to this.
Interesting scenario. If the servers are truly distinct - say, one is RP, another PVP, etc - I can see how having them all on one thread would be maddening (different populations, discussion topics, etc). So, I'd say its situational - if you can provide details showing these distinctions and then those actually play out in reality, I'd probably say its good to go. Do you have those details fleshed out?