z32type

I recently purchased a 2003 Lexus IS300 Sport Design with 140k+ miles car is in great shape with just minor things that needs attention.

1. The traction control light is on and keeps flashing every 3-4 seconds. Pushing the traction control button doesn't help. I also noticed the car on certain cruising speeds or hitting some bumps
feels slippery like its about to slide off to the right.

2. The steering wheels vibrates while braking on higher speeds above 40 mph possible rotor replacement? I went to Autozone and they have check for codes. It ran a C1202 something about ABS. One of my friends said the brake fluid is pretty dark or sensor could be broken.
Could it be related to the traction control flashing? But the ABS Light is not even on.

3. 1st time changing my oil last night I decided to go with a Mobile 1 Syntethic High Mileage 5w-30 six quartz. I know the recommended is 5.7,but I decided to do the whole 6 is that fine? I checked every time if this car leaks before or after driving it. No leaks until I did the oil change I noticed some oil leaks through the drain bolt after time. I'm sure I tighten that bolt down pretty good even gave it some hand torque. I'm also using a mobile 1 oil filter. Do I need to replace that bolt every after oil change?

4. Last but not least I also have this weird light on my cluster. I can't really pinpoint what it is,but I did check it out. This isn't my car,but I took it off someone else on google images

Its always on and something about auto leveling light. I did check my headlights if I'm facing the front side of the car with the lights on. I noticed the left front lights are more brighter than the right side. Is it related?

Any feedback will help thanks!