Hi,

The IB long haul J class is pretty good ( now fully horizontally flat beds ) although last year when I flew to SCL in Chile they only had blankets ( no duvets). The food is pretty good ( better than BA).
In JFK you will be flying out of T7 and be able to use the BA lounge.

1 hour 5min should be sufficient.

I flew SCL-MAD-LHR with a 2 hour connection at MAD last year. Due to a problem with the electrics for the seats we landed at MAD 2 hours late but there was an agent at the top of the boarding ramp with new boarding passes for the next flight to LHR ( leaving an hour later) and the checked bags made it to the new flight.

Regards

TBS