3500 RPM as a shift point shouldn't be any concern. That's still the middle area of the rev range. You're driving a car, not a big tractor trailer. If you keep the revs low all the time you'll tear the engine up, it's counterintuitive, but it's one of the WORST things you can do to an engine next to frequent idling.

You have the bowden cable adjusted properly when the transmission is shifting ~4300-4500 RPM at 2-3 and 3-4 with your foot welded to the floor.

When shifting properly, the shifts should be firm, but not jarring. If it feels like a cushioned slush box, you have it too soft. You mentioned earlier that your VCV is disconnected. Being an '85, you need to make sure the vacuum lines match the original vacuum line diagram for your car. That includes the one-way valves and restriction orifices. The VCV and blue-UFO together control your shift firmness. At light throttle, it softens the shift, at WOT it makes it firmer.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]