"You're in the slot" means, i believe, you're on the correct glidepath.
"50 above" is the TAWS warning - 50 feet above the terrain right below them.
"Decide" - your at minimums for the approach, continue or go missed.
"430" would be the descent rate in feet per minute.
You drop the gear when the flying pilot asks for it, generally around the outer marker or final approach fix (in this case).
Flaps are added as needed, so maybe he was a little high and needed to come down a litter faster without gaining too much speed.
Hope this helps,