1300 hp mercury comet brake failure crash

My (425 ft/lb) twin turbo BMW diesel does 80MPH at 2000RPM. (335d) (assume throttle stuck there) Of course that's in 6th gear. If I ride my brakes...to get down to 40 MPH, well I cant see them lasting long...and it has big 4wheel disks. Mind you I'm not trying to stop yet, I could, but I'm shooting a video.
Now my brakes go....
If I drop down to say 2nd My RPMS go way up and now engine braking...I still have a big problem.

And then assume I have to put it into park first in order to downshift every time lol...

The dude screwed up- good luck out there and be safe.