I tried creating a tournament but I have a whole bunch of people who haven't replied and now I can't forward any more invites. Is there a way to uninvite those who may not be playing anymore so I can invite others?

Im afraid its a problem that we all have to deal with :/

Only if it is fourth down and you are out of field goal range.

you should ahve gone to your invite list and removed the inactive oens earlier

I'm a Canadian so we don't get 4th downs. :)

I didn't realize I'd get stuck like this. I guess I know for next time.

you may always delete the tournament and recreate it

As Pink said, clean up your invite list.