This was a pretty long but intense series of events, so it was important to post them closely together so my readers, a docile bunch, don't get pissed off.
They can also have short memories, since I did a similar thing at the end of St. Vincent.
I'm not sure if this has come through as well as it should have, but Darius likes to be the center of focus, not that he needs all the attention, but he likes to be seen as the older brother who's more or less at the apex of things. In that, he emulates Brad. So when Will goes off on this tangent, it's probably going to piss him off, because Will's stealing the limelight. He'll view Will's trashing of the house and running away as ridiculous stunts to get attention, and probably view them scornfully.
Jeff and Matt haven't slept together, but good guess.
I think Darius cares, I just don't think he gets how much things have changed around home since he moved to Paly.