Test Runs by Requirement - measuring test coverage

Hello, I'd like to measure the test coverage (%) for individual releases and requirements. 

I have created the following relations:
Release - Requirement

Requirement - Test

Requirement - Test Set

Release - Test Set

Eventually, it occurred that filtering in this dashboard doesn't work as expected. Actually it shows all executed runs, Release is not respected.

Screen 1: Dashboard: Release filter applied.

Screen 2: For a checkI linked only 1 test. Here is the run history of this test.

Indeed, in total it was executed 7 times but against this particular Release (TEST-3.2.8) only 1 time.

Assuming that this Dashboard chart (Test Runs by Requirement) will provide correct information.

I can see absolute numbers only. Is there any Report behind it, I could export as Excel and easy pivot, so to calculate % coverage?

Also linking all Tests to Requirements is quite cumbersome.

I checked it and it's mandatory to link all Tests. Initially I thought that linking Tests Sets only will suffice. Unfortunately not. It would be a good feature I suppose, since we already have a relation between a Test and a Test Set.

How do you measure test coverage, using QA Complete?

Thank you very much!