My guess, due to the large crowd and fewer sniping spots, is that these three challenges in combination are not possible? They were on the two previous episodes. But I have not found any information confirming or denying this.

Excuse my sneaky rant insert- This is where the briefcase would come in handy... All of the briefcase naysayers seemed to have thought that adding it would make it too easy. Episode three would have been perfect. They should simply make guards suspicious of you (possibly even immediately moving to arrest) carrying a briefcase after the first sniper hit, adding some level of difficulty whilst still allowing you to still move through the NPCs.