My positive battery connector is loose and won’t tighten down any more. Can I replace the positive cable or is there any other options I have?

 

You've got a few options here:

Cheapest is to remove the cable, get a hammer and lightly tap the lead-electrode to flatten/squish it. This makes it shorter but fatter and for most situations will widen it enough to clamp onto solidly. ****EDIT: OH BTW, REMOVE THE NEGATIVE CONNECTOR FIRST! THEN REMOVE THE POSITIVE!**** (when reinstalling, Positive then Negative, opposite order)
Second cheapest/easiest is a battery terminal sleeve like this: which just fills the gap. (Make sure you get the right size)
Most expensive and pain in the ass is to remove the connector or cut the cable, and replace the connector... but honestly don't do this if you can just do one of the above.