I would not recommend very low settings such as 3 for a non-power vented stove. Remember you need some heat to make the chimney produce a draft. As Dave said make sure you have a functioning CO detector and I would also recommend a manometer to make sure there is no CO problem.
Having said all that, one trick to get the lower settings to work is reducing the amount of combustion air entering the stove by either reducing the speed with a rheostat or covering part of the inlet with aluminum tape. The most accurate way to do this is to measure the draft while making the adjustment, you can also drill a small hole in the stove body above the ash door to directly measure the effect of the change.
Have fun with the science project!