[Remmy700P]

I'd start with this list:

1. You need to find out where the coolant is going. Do a complete coolant flush and closely monitor level. Make sure the drain petcock and radiator cap aren't leaking.
2. Replace both front fuel-air sensors with Denso O2 units.
3. Check your brakes. The pads are probably gone and your brake fluid reservoir level is setting off the light. Assume the rotors are probably shot as well.
4. Replace spark plugs. Inspect ignition coil boots closely for rips/tears.
5. Replace gas cap. (Trust me on this).
6. Have the AC professionally inspected/serviced.
7. Replace engine intake and cabin air filters.
8. Change oil/filter. Have sample sent to Blackstone Labs for used oil analysis (UOA).

Clear codes and see where you're at. The VSC/Trac Off lights might be the ABS unit. That's expensive. Cross that bridge later.

 

[Remmy700P]

The coolant "overflow" tank is a fluid thermal expansion capture vessel. It will fill up and empty as the coolant heat cycles. it's perfectly normal. It should fill to the "Full" level when hot and drop to the "Low" level when it is cool. Are you able to drive it several miles in stop-and-go traffic after warmed up without it overheating?

That wiring looks scabbed in to me. Not sure where it is supposed to be connected to from your pics. The inline fuses imply they would be attached to the positive battery post, but without knowing more, I wouldn't want to suggest that without a deeper tracing of the attached wiring.

The ABS fault codes indicate a power supply problem with the ABS control unit itself as well as one or more solenoid failures within it. I'd get your random wiring nailed down first, THEN address the ABS/VSC codes. One might take you halfway to solving the other.

The silver lining here is that the vehicle doesn't absolutely need the ABS unit to have braking function. You just lose the safety aspects of the ABS system. Just be aware that hard braking could result in locked up wheels.