While the shot should've been a bit longer to convey that, in my humble opinion (taking into account director's comment), the last shot shows the same man we know, but a man who at this point of his life has nothing to live for.
His hand lies open on the table - he is looking for a new meaning, for something to live for after what he's lost, after what he has done.
The color scheme - light/shadow play - implies that he is "nowhere", he is in a metaphorical purgatory. Still has hope, but it's all but abandoned.
This movie, again only IMHO, is a very flawed modern "Deer Hunter" (as it itself implies) - a violent tale of inherently good men who are forced into violent and inherently bad circumstances - that also serves as a (heavy handed) metaphor for the current state of things.
And the last shot shows just that - "I'm too tired to go on as I've been through the worst - but I try, I try to have hope and look for something, though "best" it will never be".
Edit: I first wrote "the last shot shows a changed man", but quickly figured it was a poor choice of words as he is not a "changed man" as the phrase usually means, but a "changed man" as in "ruined", "lost in his beliefs and sense of self and the world around him".
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