Getoutofmygalley,
Although I think you were not very nice to the people not paying any attention and then asking question (at the end of the day they rather be told once again where the exit is rather than block an emergency evacuation), I really liked your idea about asking to put on the life jacket. It is on the top of my "to do" list on the next trip.
Now as a contribution to the tread, I think is a good idea for the person making the PA to monitor the cabin or the crew and stop the PA by requesting the pax who do not pay attention to do so. An idea somewhat difficult to solve.
Rwy in Sight