Did you check to see if the golem had the superheated condition before using the hammer?
Also, the Nere fight is difficult, but it's doable. Personally, I enjoy the challenging fights. You mentioned watching some videos to see how others approach the fight. I think that's a good idea. It might help you with your next playthrough. One thing I would definitely suggest would be concentrating on the mind duergar early, removing them as fast as possible.
