The Friendship between Danny and Flack is, for me at least, the best part of the show. The Danny/Lindsay shippers need to face it, the friendships between the characters and the cases themselves are the heart of the show, not romances that have very little chemistry.
Since the friendships are so important to the show, I think Danny will be there for Flack, it's probably going to make Danny feel uncomfortable, but I bet he'll be there.
And about the whole Danny and the emotional breakdown thing, I think he has to have one. He's been bottling things up this season, like what happened to Louie (Come on, one cry on Mac's shoulder does not alleviate the distress) then Stella is attacked (You know he's close to Stella, so of corse he had to be worried about her) then Aiden is murdered (he was surprisingly calm about it, one outburst about a suspect isn't like the Drama Queen we know and love) and then the bombing happened and Flack gets hurt (One meaningful look into his hospital room doesn't even begin to cover how emotionally distressed he has to be by now) I mean after all, he's only human. And humans can only take so much. After all that, excuse me while I quote Katee Sackhoff from Battlestar Galactica, "If you don't scream, you're crazy." You'd have to be crazy if you didn't react in some way, like trashing an apartment, or going out and getting drunk.