Assuming that you are sitting in the front or close to the middle door and you get off first you can do it in 1 hr 10. The issue is the time of arrival. After 1 p.m. there is a flight every 20 mins or so packed with tourist or returning residents coming for holiday. If it is around 5 p.m. no chance as you have the ba, virgin thomas cook and a charter on the ground at the same time.

I believe the AA lounge is still closed but not sure. Once you do exit you have to come out and turn to the right and enter the departures building

Hope this helps and greetings from sunny jamaica