Blackwire plays dumb. "Not quite sure what I know about all that, but maybe my captured second-in-commands hung onto the intel better."

Nevertheless, he does give basic information, just to bait the hook.
His previous allegiance was run well enough, carefully developing methods for seasonal raiding - including a pattern of establishing safe houses and operating bases in preparation for raids. They made sure cells of raiders were separated enough to stem the loss if one gang got captured, wiped out or defected. But the separation was never too complete to prevent information leaks...
He thinks this "Mailer" character is some kind of urban legend that the generals encourage to raise morale and keep defection low.
He's never been to a Shelter. Only scuttlebutt tells of this or that gang raiding a Shelter, but nothing concrete.
He's definitely set up mutants to attack settlements in the past.
Blackwire never used, saw or wants any Old World WMDs. He does not think the generals or anyone else in his organization has access to such horrors, or they would have used them by now.
He occasionally oversaw gangs that went into The Gutter, yeah. Never ended well...