I made some progress so I thought to share it in case someone else might run into the same problems.

I copied over the inv.b* files from a different savegame into my last one and all my skills and story line is preserved and I can play. Unfortunately it wiped out my entire inventory so I don't have certain items that are very important (like the teleporter scrolls and letters). Does anybody know of an item editor for DD? It would help me get back my items!!