Fog lights/horn not working

For the fog lights there isn't much in the circuit but the TIPM the wires, bulbs and the grounds. I would probably start by using a test light at the bulb connection. Turn on the fog lamps and check for battery voltage on the white/yellow and white/orange wires. If you have power there then it could be a bad ground as they both share the ground connection. To check that you could simply find that ground in the left side of the engine compartment and verify it isn't corroded. The horn relay is also part of the TIPM. Both could be bypassed by adding in new relays but I would check that the grounds are good and that the horn itself works first. Testing the horn only takes a jumper wire to battery positive from the gray/yellow wire that feeds the horn. It could have a bad ground as well and it grounds through the bracket.

I wish I could. None of the diagrams of the internal parts of the TIPM (relay box) are available to anyone but the company who makes them. There are a few places that rebuild them, but they generally open them up and just replace all the relays and parts that are known to fail. I've repaired a few of them, they are really not that bad if you know how to do board level repairs. If you want to see what they are like internally there are a few good videos on youtube showing them apart. This one shows the guts pretty well, but yours is a bit simpler:
https://www.youtube.com/watch?v=a7gEDHsppEs

These are all the wiring shown for that relay block. It looks like the 25 amp fuses power the heater system but the OE diagram shows two 25 and one 50, while your box has one 25 and two 50 amp fuses.

For the steering angle sensor, it will need to be calibrated and the system reset. If it is off it can turn on the traction control light as it will disable the system due to the error.

The 2 volt drop on the fogs shows you have a problem, Probably corrosion in the system either at a connector or the wires themselves. The issue isn't so much voltage as current. That is why a meter works but using a test light with a higher load works better. To explain it, think about what the wire does, a single strand of very light wire will show correct voltage, but that single strand cannot carry the amount of amperage needed to light the lights. So they wind a few strands together to increase the amount of current the wire can carry to light up the lights. In your case the wires cannot carry that amount and you get no lights, plus as there is an issue it also is blowing the fuses. I would trace the fog light wires back, you need to look for damage, rust or other reason why the wires cannot carry the proper current. It's one of the reasons I try to use a test light in situations like this, the loading makes a difference, in your case the fog lights are the test lights. As you are going to school for this you might want to ask about voltage drop and what it means.