I wish I knew that chicks can survive 2 days in the incubator after hatching without food or water. My first of MANY mistakes was taking them out as they hatched, I screwed up the later hatches and only the first chick survived. You are starting out with one of the best incubators so all my other problems won't apply to you. I wish I knew that still air incubators are trickier to deal with (added a fan for later hatches) and I wish I knew that too hot was worse than too cold.
Make sure you have enough room for the possible chicks that will hatch! My first time, I didn't think of it..... I just got greedy and every egg that was dropped from the hen, I grabbed it and tossed it right in the incubator! Come to find out, all the eggs hatched, except for one who tried to break out of his shell but couldn't make it out and died, oh how I still miss you to this day and asked myself what more I could have done to save you. Maybe perhaps you saw a small glimpse of this world and figured it all out, that it was too cold and too cruel for you to live in..... whatever the case may be, rest easy Little One, you shall not be forgotten.
I just bought that exact incubator, and fertilized eggs are en route. I share your concern about the humidity control. As I understand it, you add enough water to maintain half the water pot full until you're 2 days from hatch, then you fill it up so both halves are full. The included instructions leave a little bit to be desired... That still doesn't leave you any way to actually measure the humidity. That aside, it seems like a really solid and well thought out device. I think I'm just going to trust it to work.
Humidity is fairly easy, keep it low for the first 18 days and very high the last 3 days (for chickens)... for me I try to start out around 50% let it get down to 35% then add a little water (not a lot) get back up to about 50% and repeat the process until lockdown. then I fill all the water spots full and get it up high. When in lock down if I need to add water again I warm the water up in the microwave a little bit then add it.... not saying that's the best way but its the way I do it. Others might tell you they do it differently and I won't argue with them because I am still learning.