Electrical issue? ABS, brake, fuel gauge

A few months ago, my 2000 fuel gauge started acting very erratic. It reads full when moving at regular speeds (regardless of how much gas is in the tank), but will usually go to empty when idling (again, no matter how much is in the tank). Once rpm level increases, the gauge goes back to full. It rarely reads anything but full or empty, and I've learned to use my odometer to gauge the need for gas.

Within a few weeks, my brake and ABS lights started coming on at the same time, but not at any particular speed. And they don't always come on, but almost always, especially the longer I drive the truck. If they're on and I stop the truck, then restart, the lights aren't on any longer. They always come on together, never one or the other.

I've read posts about bad fuel sending units and faulty wheel speed sensors, but I'm starting to wonder if an electrical connection could be causing both problems. Any help is appreciated.

On the ABS light you need to get it on a ABS brake capable scanner and always check it when light is on befiore you turn key off.
Post back ABS brake codes.
If both red and ABS yellow light is on always check brake fluid level and emg brake switch.
Have the brakes been worked on before it started doing it?

How many miles on it.
Fuel gauge problems is usually a bad sending unit in the tank or ground or wiring problem.
Some shops have a tester for fuel gauge sending unit.
They are a resistor type sending unit and pull ohms as to how full the tank is.