Where are you getting 800w? He's running 260w in lights, with a low output of 14v while running he's burning 18ish amps. Stock alt will handle that additional load easily. But you should be running that load through a relay and not just the switch, which odds are you are doing.
But anyways an over drain is easy to see, everything will gradually dim, the jeep wont just die and leave the lighs running.
Odds are im typing on a tablet. It takes too much effort to add some punctuation. Im lazy, get over it
Never underestimate the power of stupid.