Hello Phillippe. I'm not sure about the required spacing to combustable surfaces. I believe there is a plaque on the back of the stove with those requirements.
An inch or more of foamboard will make a big difference in heat loss to the concrete and outdoors. I would also insulate the joist ends where they meet the outside of the house. [the joist bond].
In the photo the fire appears to be really going well, you should have lots of heat. The ash looks like there is no unburnt coal.
A neat tool for diagnosing these problems is a laser thermometer. http://www.harborfreight.com
has them for $40 the last time I looked. Napa autoparts stores have them too, but usually higher priced.
Your flue temps are reasonable, and your heat output is good, I'd concentrate on insulation for the basement.
Have a safe Christmas weekend!