Did the fire go out because the water temperature went above the high limit and you missed a few timed runs? If so, a dump zone would probably stop that type of outfire. That would require that you add another aquastat, such as an L6006. You might try 3 teeth and 3 air and monitor the pot. My brother-in-law goes down to 1 tooth in the Summer.
If the fire goes out and the temp is below the high limit, you could increase the timed runs and check if you have enough draft.
Do you have the outfire aquastat installed to shut off the coal feed?
It sounds like you have everything set up OK, otherwise.