Fuel sending unit

For #1.You haven't searched enough. Basic and proper for your model 5/16 senders without a return are available. At the same time, the aftermarket senders aren't correct in electrical function. Best plan is to have the OEM sender restored.
For #2. Sounds like a bad ignition switch to me. Set up a test lamp on yellow wire at starter relay. Watch for test lamp to flash as switch is rotated.