How many buoys could be stored on board in the racks on the MR.2? - MRA.Mk 4 had storage for 350, apparently….
.
This was completely variable. As you will be aware the Nimrod was not blessed with a lot of cabin space so space in ordnance area was at a premium and frequently a compromise (between seats, if you were deploying with ground crew, extra kit depending on your task, and sonobuoys.)
I expect this would have been a even bigger issue if the MRA4 had got into service, because there was even less space/seating, down the back. Not that BAE would ever have admitted that.
Was the MAD on the MR2 still the ASQ-10A?
Yes.