Dont just throw parts at it.The batt might be bad but most parts stores will test for free.After 30 years in the buisness it sound like the starter is going bad.Typically if you have to keep turning the key to try and start amd nothing its the starter going.Like I said have the batt tested.Simple test if you can get it to not start.Hook a test light to ground.have someone hold key to start while it wont crank and touch the other end of test light to the small terminal.If it lights its the starter.The old trick was to bang on the starter while trying to start.New starters usually have ceramic magnets in them and banging on them will crack the magnets.Rocky