Wow, that crafty
Nah, don't worry, if you use EasyEDA it's super easy, you just drag and drop component from component list and connect them with line, one 10min youtube video how to use it will get you up and running. Don't be intimidated, its super easy hence it's name.
Are those 2 rows of switches has 3 positions? Can you link or draw their internal diagram? I'm not familiar with those switches. Also those knobs are pulse rotary encoders on potentiometers?
Tomorrow I'll will make you a simplified diagram how I would connect everything, tho as we told you - you like it or not you'll have to use diodes, any will do, even a cheap zeners
, but schottky diodes with lower voltage drop is preffered, especially for analog stuff.