From a design standpoint, the flat of the panhandle for the sideplate should be on the same parallel as the major flat of the sideplate... Is that clear as mud? Look at this fine illustration from The Luger Mechanical Features E-book by G. Henrotin.
If your sideplate is bent even slightly as the red dashed lines indicate, this is probably the reason that you are required to use so much pressure to open the takedown lever. Another less likely possibility is that the notch in the takedown lever made for fit with the takedown lever spring has a burr on it that can be polished away...
No Luger part should have to be forced into place and no tools should be required for movement of the takedown lever... Some gunsmiths bend this panhandle surface up (as the red dashed lines show) a few thousandths of an inch to tighten the fit between the sideplate and frame. While this is functional, the problem is really that one or more surfaces is worn past a good fit... this fit should not be such that it interferes with proper takedown procedure. Use of a screwdriver to open the takedown lever will ultimately result in a major scratch on your Luger when you slip during the process. Get a good Luger gunsmith (like Hugh Clark or Ted Green) to adjust it for you if you are uncomfortable with bending the original sideplate yourself.
regards,
John
http://boards.rennlist.com/upload/Plate.jpg