My spare tire is gone. I don't know if the cable broke or was cut. Is there a better replacement system for holding up the spare tire than just replacing the current system?

The cable is sufficient to hold the weight of the tire. Someone probably cut yours and took your tire.Aside from putting the spare tire in the hatchback there really isnt another option. They make locks for the hole in the bumper, however that wont stop someone with bolt cutters from cutting the cable.

The older model fords had a metal plate that would drop down and you set the tire on it and then pushed it back up and you could put a padlock on it. IT may be too expensive to modify than to just replace your tire.