Gas Gauge The gas gauge doesn't read when the tank is full but will start reading when the tank is about 3/4. Plus when I brake abruptly the gage will bounce up and down and sometimes will stop reading. The gage always resets each time the car is turned off.

Hello,
the problem could be in the sending unit. this is a wired potentiometer and if you have a broken wire in the potentiometer, then that is what would happen.

you can verify this by grounding the sending unit wire to ground. you will have a full tank reading always. then use the car and see if it will still bounce and very erratic. if does not do that, then the sending unit is the problem. if it still do the erratic reading, then there are more problems.