1- I have few friends = I am lonely
I have a few friends= not many, but enough
2- Use the singular as it functions as an adjective. however, I'd say 'student parking spaces' or the first.
3- John's choices
With Guantanamo, I'd use the dilemma of Guantanamo- the dilemma is associated with Gitmo, but doesn't belong to it in the same way. 'Guantanamo's dilemma' is a possible phrase, but not likely to be used, but the 'Guantanamo dilemma' is fine.