Welcome to the forum. I've never worked on a 300E, but I suspect the whining noise is likely your power steering pump because you said it makes the noise when you are turning the wheel. If it is low on power steering fluid it will make this noise.

I think you may have a different issue going on with the vibration at speed. Check for the obvious first, like make sure all your lug nuts are secured and tires are not damaged. It could be just a damaged tire that is vibrating at certain speeds.

As for the oil consumption, if the engine isn't leaking, then it is likely burning it. You should check for oil leaks and, if none, maybe do a compression test.

Seeing the oil pressure drop down to 2 is probably normal. In the summer in Arizona, my oil pressure on my E420 goes down to 1-bar at idle. Also, 80C is the normal operating temp for my E420 and I would guess it is normal for the 300E as well. Maybe someone who has some experience with the 300E can chime in. I hope you make it home okay. I would consider driving in the right lane with flashers on if you are that concerned. Can you position the car between the street and a curb to crawl under and take a better look?

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles