Firstly, congratulations on almost two years remission, that is wonderful!
Nice idea of your husband to get you something as an enjoyable hobby to keep your mind on
This is a hard incubator to get right, but once you figure out its ways, it does alright.
Rubbish instructions for sure.
I got a digital hygrometer off the internet to help get mine sorted, its worth doing, cos the temp can be off a bit, mine was off by about two degrees, you'll need to calibrate it correctly.
I've pulled the little mesh circle out of the airhole at the rear so I can feed the temperature probe down into the incubator. Then you make sure it is sitting at the same height as the inbuilt temp probe.
Then once you get an accurate reading of the temp from your external hygrometer or thermometer you adjust the temp on the incubator.
To do this:
First take note of the exact temp reading the incubator is currently reading.
Push SET for 3 secs to enter the menu, then use the plus or minus button til you get to the code saying 'CA', this is to calibrate temp.
Press SET again (just a short press this time) to enter calibration setting.
Add or minus points of a degree to equal the reading from your external thermometer.
If you leave it, it will exit the menu screen on its own then and should change the internal temp until it will be now reading the same as the external thermometer.
I leave mine on 37.5 degrees from start to finish with good result.
Also, don't worry about opening it to fill the water channels, the hen would get off the nest everyday for a forage anyhow, it doesn't hurt them.
Pour water into the smaller sized channel only, every few days or when the humidity drops enough to set off the humidity alarm.
Pour water into both channels for the last few days of lockdown and don't open it anymore.
I hope your hatch goes well, good luck!