I was unable to break it loose with the truck in 5th gear, that bolt is spec'd to 210 or 230 flt lbs, IIRC. I disconnected the coil packs to prevent the truck from starting, and used the starter motor. To prevent the breaker bar from flying off, I simply did a quick, single wrap of duct tape around the handle and the frame.
I've heard of a few people getting it off in gear, as you describe, but for many, it is simply way too tight.
Baby Beast 2- 1999 4Runner SR5
Baby Beast -1987 4Runner SR5-Gone, but not forgotten