my main problem with this web page is regarding the temperature that is generating the draft.
A system using a stove is a closed system. I have seen when starting with no fire, draft has to be established. In those cases, I usually take newspaper and start a small fire in the stove with them. It has never taken long for the draft to start even when initially the draft is reversed at start-up. This used to happen to me a lot in the fall during start-up in one house I used to live in. Start small with newspapers and not a lot of smoke comes in the house prior to the draft being established. A fire, even banked way down, is hundreds of degrees - going strong - in the thousands of degrees.
I have run fires inside a house also with open systems, like fireplaces. I used to have an open fire in my kitchen where I could cook next to my stove. I've barbecued in it in the middle of summer and outside temperature was above the inside house temperature. In the most difficult scenarios, I had to hold the burning paper up into the entrance to the chimney with tongs until the draft would be established.
Natural draft up a chimney with no fire and the natural draft up a chimney with a fire are distinct in the temperatures you need to use to calculate the draft.