Brakes suddenly locked up/stopped working

96 Blazer, and now, when applying the extremely firm brakes, truck stalls out (even if parked)

Had brakes replaced about 2,000 miles ago. No apparent problems since until suddenly they stopped working. It takes both feet to compress (with strong legs), compression of the pedal is accompanied by a loud whooshing air sound, no "Brake!" Warning light comes on, and replaces old dry-rotted hoses did not make any difference.

Also, since this issue started, when the brake is depressed, the engine (which was just replaced approx 6,000 miles ago) kicks and bucks and then stalls out if held for too long (such as at a regular interval stop light). Since it hadn't done that until now and it only happens while using the brakes (not while in Park) I cannot help but think they are connected issues. I've never experienced this kind of issue with any vehicle before so I would greatly appreciate any input, suggestions, and/or ideas as to what it might be.