There's an access fee set up by the man/family in charge of the land that was 200DKK (around €27) last year, which is quite steep but at least includes a well-maintained trail and basic facilities like a toilet and I think little cafe. The entrance hut may or may not be manned if you go at crazy hours, and you may or may not find a place to drop the cash if no one is there.

As for camping, I'm not sure but I know that the Faroes are generally quite strict as to where you can camp legally. Fishing I believe is permitted, with a permit. Best doing some research.