Break your project down into small steps. Accomplish one then move on to another. Everything you describe can be done with Arduino devices, I really don't see the need for a Pi. You can run a web server on a $1 ESP board.
You aren't really painting a comprehensive picture of what you want to accomplish, but a lot sounds like 1980's technology.
You don't want to depend on an OS? What do you think runs on the Pi?
Why are you afraid of WiFi?