Your setup is pretty cool!
I won't be able to help with most of what you want but I have a little.
I have been using a Govee Bluetooth Hygrometer and Thermometer
these past 2+ months. I originally had it in the vivarium taped to the cieling but it fell down (double sided tape didn't have a larger contact area) so I put it on top of the vivarium on a screen vent with the sensor hole facing down. I calibrate and spot check the Govee with a more precise
hygrometer. What I found is that there is almost a 10 point difference in humidity between the bottom of my tank and the top (insitu tank). The Govee sitting outside the viv reports results that tends to be somewhere around the middle the of the tank. The temperature is accurate for the top portion of the viv. Best of all it keeps track long term for temperature and humidity. Here is a days worth of data and a week.
Since its not in the viv and getting sprayed every day I have faith it will live much longer then in viv hygrometers.
Your setup also looks you are not using mistking style nozzles. I don't know how your nozzles perform but the mistking produces a very fine mist that tends to go most places in my viv pretty evenly. With as many nozzles as you have you should be getting very good coverage. Something that can be done is you could put a very large powerful fan (relatively) that only turns on when watering to blow your mist around more. There are also computer fans out there that are variable speed or you just use more of them so you could have one small fan running all the time and larger fans that turn on only immediately after watering etc. Its not clear to me in pictures if your viv has a door or not. If it doesn't then clearly that would help a lot to make sure the conditions in your viv do not always follow those of your house.
Also have you tried other types of moss for roots? Sphag is pretty much the wettest stuff out there but not all moss is equal in this regard.
Hopefully some of this is helpful.