RE: Shot or no shot?
shoot him, or come back tomorrow, 20 mins to close the distance, sounds like then you'll be closer but in the dark!
and calling to him to bring him in etc...doesn't sound very plausible, so I say shoot or come back tomorrow and try to get on him again, all what you feel confident with, but you put that .300 win mag through his front shoulder and into those vitals, I don't think he's going far, and you can probably put another round or two in him, come back in the am and retrieve him.
Course its up to you, though IMO only 2 of your 4 options were actually any I'd consider.