Amiga 2000 Video & Audio Issues

[Castellen]

Given the symptoms, it's very likely that there is at least one open circuit line in the register address bus (RGA), or possibly the DRAM data bus (DRD).  Refer to the schematic for details: http://amiga.serveftp.net/Schematics/A2000_schematics/A2000_R6_schematic.pdf

Both of these buses are common to U200 (Paula) and U201 (Denise); use a scope to check for activity on all 8 address lines at either U200/201 and 16 data lines, and it should quickly be obvious what's not working.  From there you'll be able to work backwards to pinpoint the open circuit track/via.

The register address bus is created by U101 (Agnus), so an open circuit line can be also caused by one or more bad contacts in the PLCC84 socket.

[Castellen]

But after bending all pins straight again the A2000 is back up and running again ^^

I'd suggest replacing the entire PLCC socket unless you're very confident it's perfect.  IC sockets are notorious for causing all sorts of horrible intermittent problems.

Any suggestions on other things I could do?

Depends what you want to do long term.  There are plenty of interesting options in terms of the PiStorm and Vampire expansions.