Not one to duck a challenge, but unfortunately...
There are too many theories behind the poison kill; without testing them out this was nigh on impossible in a one-shot deal. I went with the possibility that Nicola's routine might change after Caruso escapes by plane. I tried to lure Caruso faster with the '47 Ways' tape, and his two guards seem to be stuck watching the video once they settle back down after the plane has left.
After that it all got a bit
(minus the coke mountain).
PM when you can with the deets please @scm97tl: bet I was way off.