What did Rush do to the ship? Was he worried that they might wormwhole back to the earth? Or was it that it really wouldn't work and he did something to get rid of Telford?
Rush and Brody sabotaged things so the wormhole wouldn't connect to Earth...although he claimed it wouldn't have worked anyway and would've torn the ship apart if he hadn't let safeguards in place (I guess that's why teh Stargate sparked...but the alarms and locking out the Earth people was his doing).
As for the other questions, your guess is as good as mine about Rush and why if these are "the wrong people" why there's not more switching with experts to keep things going. Or why Telford went to the door at the end.