I think that you're right the car probably has many bad electrical connections , especially bad grounds and connections in the charging system, plus it could have a loose connection or a wire that is corroded internally on it.
I'd go over all the grounds in the car inside the car , under the carpets , by the steering wheel , at the fuse box in the car , under the hood , go over them one by one , you may need to replace some of the grounds and wires be sure you use the same gage wire.Also go over the power junctions . battery , alternator , starter , alternator , engine block ground connections and connectors clean them with a wire brush , sandpaper , file and be sure you replace any bad wires or ground connections.
Hope that helps and best of luck.