I dont know what the ezi start set up looks like as iv never seen one before, but the way to fix a cut wire is the following.

Pull apart the ezi start assembly. Strip the insulation from the ends of the cut wire, solder it together, then put electrical tape around it. Or, you could get another wire of a similar gauge, get rid of the old one, and solder on the new one. Work out how it got cut or you'l lose this one too. Could it have gotten caught up in the gears or something ? Maybe you can get yourself some zip ties.

The engine sounds like its bogging because its running rich. Start turning the hsn in, clockwise.