If you uninstall Parallels you won't lose your Bootcamp Windows, or any other VM. Uninstall of PDM 8 is just dragging the .app to the trash. You should also uninstall Parallels Tools inside Windows.
However, if you uninstall PDM8, it won't solve that problem you are having with not being able to start your mac directly in Bootcamp, I'm not sure what's happening there, but I'm sure this won't solve it.