W210 dont use CHF in the power steering, they use ATF or the yellow/amber PSF sold by Lubro moly (undyed ATF DII)

if its hard on one side only then the spool in the pinion valve is plugged with gum or debris, you can use a product called trans tune by seafoam and run it for about 30 minutes and work the steering left to right, then flush the whole thing out with a quart of ATF or the lubro moly PSF - you can even use GM spec PSF if the unit is tired and old (GM PSF is thicker when cold by has excellent antifoam) - If you live in super cold weather ask your GM dealer for cold weather PSF, its very good stuff, OR simply use a synthetic ATF.

flushing is easy, raise the car, disconnect the return line, steer the steering left to right to purge old fluid as you pull new fluid in. Replace the fluid container on the pump as it has a filter built into it, allow the new container to soak the fluid for at least 20 minutes before starting the engine.

the shake between 65-75 mph is from sloppy lower control arm bushings (the front ones). If you put the car on an alignment rack type lift you can use a crowbar to lever the bushings, you will obviously see them flex if they are shot, they are hydraulic though.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)