RE escape slide inflation
One inflated in flight in the tail of an MD-81 being used by Barack Obama during the 2008 campaign. In the tail cone rather than the cabin, but intefrered with pitch control cables.
Obama campaign plane's emergency is detailed - Los Angeles Times
As to the qualifications of the NTSB chief - well, it IS called the National
Transportation Safety Board, not the National
Aviation Safety Board.
It investigates accidents and safety issues in
all branches of transportation - rail, bus, truck, car, boat. With briefs for pipelines and hazardous material transport as well.
Accident Investigations - NTSB - National Transportation Safety Board