What about going the other way?
I have 2 separate award flights booked:
JFK - LAX Arriving at ~7pm
LAX - SYD Departing at ~10pm
Will I be in any trouble trying to make the flight back to SYD?
Will only be a problem if your earlier flight is significantly delayed (which it may well be !).
Last Friday I had a 4 hour layover flying DFW-LAX-BNE.
Our DFW-LAX flight was delayed for an hour (something to do with ATC and the sequestration cutbacks), leaving three, but I still had time to:
Go landside to meet someone delivering a bicycle.
Wait half an hour for them to show up.
Check the bicycle in.
Go through security.
Drink two beers in the lounge.
(Admittedly we did not need to change terminals, as both our arriving AA flight and departing QF flight were at Terminal 4.)