The question of Reverb ? I look at it this way.....

Let's say you are playing a 'Standard / Evergreen' in a big band style in the hall you mentioned.
If you are trying to sound like a real Big Band, then why would you use any reverb??
Which instrument in a Big Band has built-in Reverb? Saxes? Trumpets? Trombones? Drums?
So why use reverb in a large hall? The hall itself will probably 'add' sufficient...

If you are playing in a small acoustically 'dead' environment, then the situation is probably different.
Adding a little reverb in that situation can add a bit of 'colour' (or 'color' for the guys over the pond )

Just my thoughts...........