YPAO is the room correction you're using.
You're correct to switch the speakers to 'small', but try the crossover at the fronts to sit at 80Hz and maybe 60Hz for the centre, then have another look.
The rear speakers may well need to be much higher depending on what they are, you're just setting the point at which the subwoofer will kick in - it's not a definitive science, but a good starting point.
When you look at the YPAO settings what are the levels that have shown up?
Front Left: +2
Front Right +3... etc etc?