I had a buddies car in Hawaii that did something similar to what you describe. It started out the same way... only he had to eventually turn the steering wheel about 1 to 1-1/2 turns to get the wheels to start turning! The problem was later traced to the steering box... Once it was replaced it was fine. Somebody had tried to rebuild it for him and messed up the little ball bearings that cradle the spool in there. I replaced my leaky unit in my '79 Formula with one from NAPA for about $185. It even had the nice, quick 2.75 turns lock to lock ratio!
Good Luck and don't drive it too long in the current condition... Your life (plus whoever's lives you have a head-on collision with) are worth having it checked out!