The proper tool is the Schwaben Strut Nut tool. It comes is various sizes:
https://www.ecstuning.com/b-schwaben...iABEgLpGPD_BwE
The center is held with a 7mm allen wrench. This stuff is cheap to buy and absolutely necessary if you are doing any suspension work.
The paper gasket mentioned is what's known as an isolator. They are necessary to prevent squeaks and other irritating noises. Springs will use rubber cups or pads as isolators when necessary.
I've done a ton of suspension work over the years. Assuming the B12 is appropriate to your car, it is a bullet proof install. When problems arise with it, it is either a faulty install or not using a correctly calibrated torque wrench. I use a Schwaben non-digital which is spot on calibration.
From what I've read here, I don't think any of you know what you're doing.