Is my iMac crashing because of a faulty HD that I'm not using anymore?
I finally build up the courage to try and disconnect the faulty HD. I was sorta successful.
The screen cracked a bit and my iMac is now assembled again with duct tape. But it seems to work. There was no error when starting the iMac, and it has been running now for 30 mins without issues. I will update this if that changes, but I'm having my hopes up.