The questions about this are all fair.
I'm a little old school in some of my thinking, and the conventional thinking about deadline trades for teams that are "going for it" is that you trade guys who are far away from helping you for guys who are going to help right now. Under that philosophy you would never consider trading a guy who's playing as well as Duran has been playing, because the net balance on the trade could easily be that you get WORSE THIS YEAR.
Oddly enough, the Red Sox have already made 2 in-season trades that could end up making them WORSE THIS YEAR: the Priester trade and the Devers trade. Maybe they're squeamish about the prospect of making 3 such trades.