Tell him that an alternate route needs to be found and he will insist that it is not his problem. Tell him that he/she will not move until he helps and then keep saying "Fine!" until the dwarf gives in. He will explain that the best way to get up the pass is by going under the rocks by breaking into a natural cave. He will explain that his wife, Freda, has some notes that will help. Freda lives in a house to the west, along the path.