Take the George Wasgington Bridge I95N to Exit 10 Whitestone BR toi the Van Wyck and on to JFK. It normally takes about 45 minutes, maybe an hour and 15 max. You should have enough time. The Train leaves the car rental area every 3-4 minutes at that time.
I have made Fort Lee JFK in les than an hour every time except after 5 PM and on Friday afternoons. D
Just don't leave your meeting after 3 PM. It will get backed up after 3 PM. Sadly, there really is no decent alternate, I've tried them all and they are not better.