If you don't want to buy a dedicated cable-cutter, use a sharp pair of wire cutters. There's some risk that the braided cable will fray slightly, but this has happened to me only rarely. The cable housing will likely need to be opened at the cut end, using an awl or similar tool to make the opening smooth and round. Looping the long wire will be ugly at best, hazardous at worst.

I don't know why an FG bike would be set up with only a rear brake. The rear wheel allows you to slow down with back-pressure on the pedals (no need to skid). A front brake is a "must" for basic safety on steep downhills.