Wolf-
1. Great question! Ibn Ezra points this out in Vayigash and he explains that these are actually two different locations! Ramesess was the area in which the sons of Ya’akov settled, while Ra’amsess was one of the cities Pharaoh ordered the Jewish people to build.
2. Don’t know. I know the general rule is that the segol becoms a kamatz by an asanachta, and that there are exceptions, but don’t know why.