I'm playing Grade 6 pieces / doing Grade 6 scales too … so on the pieces, I too find a lot of the metronome markings impossibly (for my level) quick, but also, there's been a couple of pieces where I did manage to get some of it to speed but found that it sounded too quick … I wouldn't worry about speed for pieces. I'm aiming for about 80% usually on the quicker pieces, that's just my random guess.
Scales definitely doesn't matter, but I would say choose a starting position and then always stick to it so that in an exam you do not have to think where to start … last thing you need is the embarrassment of running out of keyboard!
A bit cross about SingingPython's son's examiner comment - pedalling is a matter of musical taste, and I too use the pedal less than many others do because I prefer it that way. No doubt the other pieces demonstrated pedalling ability anyway, I don't think Beethoven always needs so much pedal.
As for the specific question, I would try the piece with and without the pedal, and see which you prefer, bearing in mind that neither will be perfect (but then again, perfection doesn't exist.) Which piece is it, BTW, I may have looked at it with my teacher so may be able to give more specific advice if so?