73 Dart Alternator doesn't show charge anymore.

Probably easier to get a good connection in the short term by cleaning it up.
It's difficult to join the fusible link directly to another wire.
Then do it right when as soon as you can. Probably the easiest will be to buy an new fusible link, a replacement connector and terminal.
But it may need new wire. When you're ready to tackle it, slice the insulation open to see how far up the oxidation goes. When moisture can wick in sometimes the copper will oxidize under insulation.

All that said, that connection is not reason for the high charging. But high charging will further damage it.