#1 - don't know how much play there should be in the driveshaft, but I do know that there are wide prawls and when shifting to park from drive on a hill there is a surpirsing amount of coast before the care settles. This may be related to your driveshaft play and not an issue at all.

#2 That sounds about right for the vacuum gauge. That's how they work. Pegged left in park or neutral, slightly right in gear.

#3 That's exactly how mine has been for approx 200k, always a little louder and rougher going into gear.

#4 - Can't help, except to ask if the car runs well. These cars are known for an erratic idle once in awhile. There's a million posts and suggestions. Mine got better when I replaced the Temp sensor.

#5 Had the same annoying and scary rattle from the steering damper. A PITA to get at, so I did the seeping U gasket at the same time. Suspension components wear out. You don't say how many miles, but I'll wager it's a lot. So replace what's toast and get an alignment. You'll have a nice car that makes you smile when you get in.

89 300CE 220K