Even if spraying water in (or letting it sit) will remove chlorine it won't remove chloramine.
Right, good point.
I dunno if permenant marker is safe for pond life... If you do end up filling bucket by bucket though you could make a little inconspicuos mark every 5 or 10 gallons on one corner of the pond... that way for future water changes you can accurately judge how much water you change/add- by counting how many lines you fill up from.
Good idea! Maybe even tape or something, if you could get it to stay on.
Future though- if you know how much water you need to add- add the appropriate prime to the pond... then fill up.
That's what I do with my python, although the tank is never completely empty. But the fish wouldn't be going in right away anyway, so I don't see an issue there. It's just the temperature.