spec for pump is 200 bar @ 2000 RPM, so I am gonna say your finger is not capable of holding back 200 bar.

if the rear seal to pump is bad, it leaks suspension fluid back into the engine and will dilute oil, etc. Not a good thing.

take a look here:
http://www.300sel.com/pdf/HydroSuspGuide.pdf

Struts leak internally, making detection difficult. The page above should reference flow rates for testing, but I bet it's the pump, given the new parts you reference.