A projector, yes, 4K definitely could make a difference there, but that's the tech, not the content - I can always see the pixel grid on sharp bright static objects even in theaters with digital projection - especially on subtitles but take the Hobbit as an example - it was shot on 5K RED cameras but it went through a 2K DI, so all the theaters equipped with 4K projectors must have been showing it upscaled.

And a majority of today's films still goes through 2K DIs and restoration work or at least mastering is often done at 2K too, so going 4K on the content doesn't really make too much sense.

As to that dark spot - that's there on the BD (though again, I really don't know how you guys notice these thing - I'd worked with that shot for hours and never noticed).