Hello.
I just wanted to share with you that if you want to use your tool XInputDotNet with the "new" package manager of Unity.
You can structure it like the fork I did based on your project:
https://github.com/EloiStree/XInputDotNet
If you don't know what is the package manager, I did a tutorial about it:
https://github.com/EloiStree/HelloUnityPackage/wiki
Hope, it helps you.
PS: Thank for your code.
If you have a donation link or a Paypal, I would like to send you a beer for your code ;)