I would clean the rust, dirt, remove the water and then apply an external boot over the existing boot + use steel hose clamps on both ends (you have a nice spot to attach these clamps - a nut and/or a neck behind). You basically want to keep water away from the naked cable, so any solution should work.
Stellantis vehicles are dirt cheap when the buyer doesn’t mind to spend a weekend on replacing rocker arms or fixing a wild electric issue. All other kinds of buyers are usually not so happy with the purchase.