There's neighbor's Ford car I'm attempting to help push out a driveway?

~but the BATTERY IS DEAD and will not shift out of park with the key in and brake depressed. There's also a 'Interlock IID anti-DUI breath reader' installed, but feel this is NOT keeping the vehicle from being able to shift out of park, am I right? Is this just and electrical issue? Perhaps a fuse?

It's an electrical issue. With the battery dead the brake interlock for the shifter won't let go.

Check the owner's manual if you can for a shift interlock bypass, or look for a slot near the base of the shift lever. If you find a slot any key or other blade device pushed into it will release the shifter.

But the BATTERY IS DEAD and will not shift out of park

IF that is an issue, the answer is EXTREMELY easy. Its called jumper cables. You don't even have to try to start the engine. You just have to supply enough power for the brake/shift interlock to operate.

There should be an override push switch, usually has a small cover on it. OR, jump it.

The Park lock is not electrically operated, it is manual and neither of those things should effect your taking it out of gear. Did you try turning the steering wheel after the key is tuned on?