Fog horn sound while I drive goes away when I stop

Probably a sticking piston.
You do not grease brakes!!!

Change Idle Air Motor.

Sometimes a weak idle air control (IAC) solenoid can vibrate and set up a reverberating noise in the intake ducting that sounds like a fog horn. This can usually be fixed by replacing the IAC solenoid.

Excessive use, horns have a very short life span.

P0102 -

Mass Air Flow (MAF) Circuit Low Input

You probably need to clean your MAF sensor.

For more info, go to this website/link:

http://www.obd-codes.com/p0102

replace iac valve and replace air filter

YOU WON;T EVER PASS INSPECTION BUT YOU CAN UNPLUG THE WIRES AT THE HORN -S IN THE FRONT REAR THE GRILL

As far as the gas gauge level goes, it sounds to me like it could be the float ball system that is inside of the gas tank, which is connected to the fuel pump.I dont think your guage in the dash is broke, but i could be wrong. Sounds like something in the fuel pump area

check the disc rotas they could be stuffed

This is probably a temp thing...night brings colder temps. The wiring may be failing or the steering wheel portion over the horn might harden and cause it to touch the center of the horn to make it go off.
Let me know if this helps.