First off, so far as I know from being here for a while, and my experience as a Slayer at home? Magic doesn't cure vampirism.
Second, even if somehow Jerry managed to get turn back, you really think he'll even want to be human, after all the shit he's done? My guess is he'll be slitting his wrists inside an hour - if he's even a decent guy. If he's not, he'll probably go on a killing spree, then we'll have bleeding hearts like you claiming that since he's human he needs a trial and shit.
Third, it looks like the only way to turn the others back is to stake Jerry. Who knows if magicing him human (which I still don't think can be done) would work on them, too? All this sitting around and talking bullshit is just wasting time and giving them more of a chance to turn people into vamps, or to kill them. And the Seal may sometimes bring us back from the dead, but the regular city people? Not so much.