I would try to stay encouraged. You have a issue but once corrected it should work very well. My 20 is heating my whole finnished area in my basement(about 750sqft) with enough heat left to keep the main floor around 69-70 as logn as the lows are above 20ish.
Your air leak is not in the stovepipe/chimney side. It will be in the box itself or the primary air control.
Your air leak is not in the stovepipe/chimney side. It will be in the box itself or the primary air control.