If Willow's telekinetic powers are sufficient to stake and kill a vampire with a pencil, why not at least try and use them to disable Faith and break her captivity. But Faith is a Slayer: much more powerful than the common vampire. And surely Willow was far from being the (almost) omnipotent witch that she'll be in the future. So she wisely chose caution.
When Buffy gets attacked by a spider, it zooms in on Xander and Angel, and you can see Xander clearly smiling at the intense situation.
Half way, when Buffy and Angel are fighting vampires in city Hall you can clearly see that it's Sarah's and David's stunt doubles.
(at around 39 mins) Buffy says to Willow "I can't believe it. Are you serious?" but her mouth isn't moving.
When Cordelia is insulting the schools Willow got into she refers to Oxford as "4 years in tea bag central". Most Oxford undergraduate courses are 3 years, not 4.