So smart lists are locked in when the campaign first runs.
If we call another campaign from that campaign, will the smart list recalculate at that time?
No, once the campaign is run and enters the first flow step then the membership for the campaign is already determined. If you change flow steps after that it will just change what will occur for that same group of people. So you need to do what Josh is saying and use another campaign to remove certain leads from the flow.
1. Yes
2. That would work as well. You can change the upcoming flow step while the campaign is already running (while the leads are in your wait step). You can change it to "if condition A, then do nothing" "else send email X"