I'd say he's nowhere near halfway either. But WTF is your problem? If you don't like the game fair enough, but you seem to be playing a lot of it to not like it. Surely you would've ditched it by now if it is keeping you awake at night like it seems to be doing. Try taking your rage out on a deer ffs.
Halfway ? I'd say a quarter. So would the story mission/uber-checklist in the Handbook.
I would say about half way through, yes it dumps you back on the island
I've just passed the halfway mark. So far, obscure 'comedy missions' like Cargo Drop, enema jokes, Portal references and the big shark-jumping moment I half expected. It really is all over the fucking shop.