Hello skyground,

#1 = Yes, you can rebuild that face with the seam edge to be a continuous surface and then the seam wont be there to limit the results.

#2 = Well, and arc on 2 different angled walls will have a different endpoint, by nature. Try selecting the "constant distance" option for filleting that edge.

But "looks not cool"? Usually "seams on surfaces" are not anything that affect anything. Just a function of surfacing.