What size duct for make-up air?
You'd use a 10&quot; duct that comes off of a plenum/metal box which is 16x16 to match the hole. You will find it... tricky... to try and attach a duct directly to an irregular surface like a ceiling, floor, wall, etc. (in other words, don't do that).

These are best answered by an HVAC technician running Manual S, T and D calculations after inspecting your system. The inch rows you ask about are static pressure  values based on your actual duct; you have to measure it with a manometer to get the location and value of static pressure, you will see these in inch values or inch WC values, typically.
Regarding which rows you read, I assume the PRN110 lets you choose which RPM setting to use, from 860 up to 1550 (the values you assigned to RPM in your question are actually the tip speed of the fan blades). Once you know what RPM you want to use, you know which row to read. Conversely, if you have an HVAC technician calculate the values on the right side of the table first, that will tell you what RPM you need to choose on the blower.