Question are the marker lights working on the trailer? If so check the wiring in the rear of the trailer for any broken wires for the brake...
All listed are serious issues, maybe except the upside down windshield, but that doesn't matter if it has a crack(s) especially on the driver...
Replace the 7 way plug itself because from what you saying sounds like the 7way plug is not making good contact. If you hold up on the 7 way plug...