Realism of being stranded for 4 years?
Is it really that likely in the 21st century to be lost on an island for 4 years without being rescued? I mean it was a pretty big island with a giant mountainface. An island like that would've been very popular amongst Polynesians, since most of the uninhabited islands are probably a fifth of the size and totally flat, and it would probably have a village on it if it were that big. If you look on Google Maps you'll see that most Pacific Islands are connected and at least one of the islands will be populated.
Maybe Chuck could've been stranded for 4 years in the 1800's, but I just don't think it's possible in 21st century with the way Oceania is connected. I think he could've been stranded for a few weeks, maybe a couple of months at max. Anything more than a year seems completely preposterous. A boat or a plane would've definitely gone by.