Bunch of questions here, if I've missed something however, post the question again ....
Tolerance - birds nesting on buildings are surrounded by human activity all the time and are much more tolerant which is not the same thing as less aggressive, they are just less stressed by human activity nearby than birds not used to nesting in similar environments. The Radisson pair will let me and a few others walk right up to them in the nestbox on the roof because they recognize what we are doing and don't see it as a threat. When I go to band the birds I use entirely different body language and sounds and direction so that I can get close if I have to without them automatically becoming protective/defensive.
Chicks away from the nest - six of one, half dozen of another. We have chicks that need to go to rehab and we return them 1 day, 1 week, 1 month later and we have never had a problem. In Edmonton, an unrelated fledgling peregrine was added to an already fledged nest and nary a problem from the adults. Remember Chinook and Mistral? He was away for almost 2 weeks, she was away for just under 1 and wehn we released them back at the nestbox, Trey and Princess were feeding them within a couple of hours (they came back full so it wasn't a concern).
Stress/distress - yes, the birds are stressed whenever something threatens their young or nest. Its suppose to. That's why they are aggressive, that's why chicks can fight very well at banding age, they are designed to be stressed/distressed in order to improve/increase their defensive responses. We try not to do that more than we have to. If the parents can't see the chicks during banding, they don't call out as much, if they don't call out, the chicks can't call back. Some nest locations are easy to access so its scoop and run and band out of sight. We do that with the nestbox. With other sites, access is more difficult, so you band in situ because its just too much activity to not be more stressful than we'd like.
PR - in the US the peregrines have been pulled from the "at risk" entirely so there is no federal endangered species funding for them. They may or may not be considered an "at risk" species in individual state. Recovery efforts take money and time. Peregrine webcams are very popular and very very expensive. The educational value is priceless however. The trade-off is that they can generate interest in wildife, habitat protection/preservation and stewardship with webcams and charismatic species like peregrines but it costs cash. Live events like bandings can raise the profile to another level which can help out financially as well. So catch-22 perhaps - ya need money to make it work, you need to work it to make the money.
Did I get all the questions/concerns?
