I feel I am rambling
I do to.
Load PD patch onto Arduino?
You can't do this. A PD patch is useless as far as the Arduino is concerned, no matter how you try to get the patch to the Arduino.
wondered if there was anyway to eliminate the computer
Lots of ways. Some more effective than others.
basically have a bootloader/script that starts up when you put the power on.
The power on what? The Arduino? It already has a bootloader, and already runs whatever sketch is loaded when it is powered up/reset.
I literally have no idea where I start, whether it's as easy as loading a script onto the chip or having a USB drive with an OS on it.
Start with taking a deep breath. Breathe into a bag is necessarily. Hyperventilating isn't helping.
A USB drive with an OS on it COULD talk to the Arduino. But, where are you going to find such a device?