OK, lots of questions, I'll answer the ones I know about.

Power steering fluid - I only use MB fluid - I may be throwing money away - and others will comment - but when I bought my car I had a PS leak. It's been repaired so I don't add fluid any more - yes, just top up the canister.

Rough shifting, could be an adjustment needed to the Bowen cable or a vacuum leak, bothe will do it - I've had my tranny rebuilt and have spent a few trips back to the workshop to have it adjusted.

Brakes, could just be a sensor on the ABS - could be more - have you tried an emergency stop to see if the ABS kicks in??

Brake symbol on when the park brake is off - check brake fluid, or maybe the sensor in the brake fluid resovour (unlikely).

Your oil pressure gauge should not drop below 1, 0.3 is almost at the bottom of the gauge.

Don't know what is in that pic you posted - but it's been a long day with a mini cyclone and loss of power for 5 hours, so I'm going to clean up around my house!

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1988 W126 420 SE

beware of fundamentalists!