How can I share variables between a Facet and RunConfiguration?

I am trying to built a plugin to integrate a 3rd party tool. Currently, I have a facet where I store the 3rd party tool's root directory. I am trying to develop a RunConfiguration that uses the root directory variable stored in my facet to run the 3rd party tool. My questions are:

1. How can I go about doing this?
2. Is there a way to store my shared variables (in this case my tool's root directory) in a central storage which I can use across my facet, run configuration, and other future features of my plugin?

Thanks!