The temp at the surface of the stove should be around 500 to 600 degrees. If you need to have the damper open to maintain that, then you may need to open a window a bit or ask the stove shop about an outside air intake for the stove.

But what are you burning? Pine? Oak? Maple? Birch? How seasoned is it? Does it "sizzle" when you open the door of the stove?

Also keep in mind that outside temperature has a lot to do with chimney performance and draft. When the temps get up in the 50's and above, my stove tends to get "lazy" and I have to keep the air vent open a lot more than when the temps are in the 30's.

This may be totally irrelevant to your post, but I'm not sure what your weather is like right now.