Same dude, the issue is the fact that gfn does not let you use all of the keys, so when you press F8 or Fn Shif F8 it actually counts it for YOUR PC instead of gfn's. So yeah you wont be able to use it on GFN.

im not sure what ur problem but if ur having problems with -preventhibernation

when u open ark from gfn it opens steam page first just stop the game before it launches so gfn wont close then add -preventhibernation then press play