KDP Select advice please!

I am preparing for a free days on my first title in KDP (let's hope it would be the last one). I read Chandler Bolt's book and he urges to start with 2 days and if the results are very god, say a lot of downloads to cut it off on the next day but to inform all sites about the two days. In Let's Get Visible, David Gaughran writes that if you have less than 1000 downloads on your 2nd free day to stop the promo and save your free days. I submitted to Read Cheaply, FKB&T and other sites with two days only, hoping to create scarcity in the customers, am I right?
I wanted to submit to Bknights the third day to be able to track the results from him only but if I have less than 1000 downloads, I'll have to cancel, so why better to include in his bid also two days.
Do you think that a very successful free promo in fiction can lead to the great results authors in non-fiction enjoy? I have to say that non-fictions tends to sell more and better than fiction.What say you?