Rescue hover pitch is selectable from 0 to 100%.

Is that a percentage of total pitch range or of positive pitch range?

If set to 0, is that full negative pitch or zero pitch?

If set to 50%, is that zero pitch or 50% of positive pitch, e.g. 6 degrees if max pitch is 12 degrees?

Depends on how you have rescue set.
If set to normal it will roll upright and give you 40%(default) of your positive pitch.
If set to Acro it will give you 40% positive pitch if upright, but if inverted it will give you 40% minus pitch....
You would need to try this to make sure the % selected would allow your heli to hover...