Electrical Gremlin?

I have a 68 Dart Convertible that has two concerns at the moment regarding electrical. First is the top switch....here is the scenario, the car is running fine and I jiggle the top switch because I notice the amp meter is not charging and the car suddenly dies with no power going to anything at all, not even the dome lights. After some time or if I disconnect the battery and reconnect it, everything works again. Second issue is the fuel gauge has been replaced with several good working gauges but still does not read correctly (always shows overfill) Can this be caused by the in tank sending unit?
I appreciate any help you can give!
Thanks