Man you guys drag a lot of stuff around! Pliers? Pencil and paper? Protractor? Don't forget the handheld jigsaw, hammer, nails, and wood glue.
The little stuff saves shows when stuff happens, and it always does. The multi-tool is standard fare for stuck threads or when a screwdriver or pry bar is needed. So is a flashlight and tape. I use screens indoors in case of ceiling fans and also on the very rare occasions someone trips on my stand and the mics hit the deck. The screens are great shock absorbers.
I've never bothered with a protractor. Here's a tip...at home spread your fingers out as far as they can go and measure between the tips of your thumb and pinky finger. You won't be too far from 20cm but whatever your personal spread, you can use that to get spacing pretty close.
For angles, 90 degrees is easy to eyeball using floors and walls to help with right angles. Then if you want 110, just set your mics at 90 degrees and open the angle just a little bit more on both sides. Close enough.