He didn't dox an FBI agent or his family (indeed, he's charged for his speech and there's a motion to dismiss that indictment on First Amendment grounds too); he was under duress and coming off meds, and outraged at the legal threats against his mother. The allegations are "conspiracy to dox" rather than any successful act. Literally they said that someone did a Google search with the goal of making "restricted personal information" public.

He flipped out and lost his cool over constant government-sanctioned harassment. He's not perfect by any means—admitted substance abuse problems and a big naïve/foolish/arrogant streak—but still deserves sympathy.

I don't think he would have known there was a law on the books making it illegal to dox feds. Doxing abusive cops on the other hand is legal and happens all the time between Anonymous/Occupy and even journalists do it sometimes.

In order to convict on threats there needs to be a "true threat" of physical harm, a non-conditional statement made to a specific person. All he said was "if they come" he wouldn't be able to tell FBI from Zetas so he'd exercise self-defense. And he explicitly clarified when he said he was going to ruin the guy's life, he meant to expose him, not as a physical threat.

One can disseminate a link without knowing whats in it. Brown is on the record in many places as being opposed to spreading credit cards. He was against that kind of stuff.