I think that the gman is an alien of some sort that is in a host body. That is why he talks funny. Also it could be that he talks like that because they try to build up suspense and a feel of overpowering 'evil' from him.
The ending was ok as long as they give us a good sequel, not ala Matrix: Revolutions, no offense Matrix fans, but they asked more questions than the gave answers to. Not to give us all of the information, but at least fill in most, not all of the gaps in the story at the very end

Oh well there's my $0.02