Please help with the doors!

It’s been a month with my DS7 and I’m mostly happy, but I’m fed up with the awful sound from the basic speaker system, so I decided it needs improvement.
The woofers actually sound pretty decent, providing a reasonable amount of bass, but mids and highs are terrible, with plenty of distortion and sound coloration because of uneven frequency responses.
First culprit, the low end quality of the tweeter.




Ok, it’s easy to replace, once you find a good candidate. But to get a flat response, installing a crossover is a must, and that requires taking the door apart. So I tried my best (reasonable previous experience), but I got stuck before fully detaching the panel.





That last photo shows the panel attachment point I can’t get to release. I’m afraid of breaking something, can someone help me please with some advice?
What about the lever? It seems to be fixed to the panel too.