2) why are you using a 128gb usb when an 8gb one is fine to install mint
3) why would anyone pay $135 for mint on a usb stick from a stranger?
Freedom is waiting for you.
I appreciate the passion that you have for this project as well as the choice of OS. I already use mint and recently pop, so I am not your target audience.
I see ads occasionally for what I assume are scams such as "Xtra-PX" that (like your product) seem to be linux running on a USB stick and asking upwards of $80 (you want more than $130) for something that is essentially free.
So, I guess my first reaction is that I don't imagine your pdfs are worth the $100 and attempting to sell that here on a site dedicated to "hackers" seems like the wrong approach.
I wonder if there is a market for something like this in corporate IT shops that are looking/hoping to move to linux from windows.
Best of luck with your project.