If the engines are at flight idle-they are still delivering thrust.
Yes, but not much. CERTAINLY not enough to stop a landing-configured aircraft on a 3deg glide-slope from stalling.
In those conditions, I think its fairly safe to say the autopilot was on-although of course one must wait for the report to confirm it.
If he was capturing the GS from above, below platform altitude, I think it more likely that the A/P was off.
the only way to do this with A/P on is-
Select a lower alt on MCP
Select a Vertical mode( Probably V/S)
Set a value for V/s
Wait while the aircraft gently responds
Wait till G/S captures
Reset MCP to Go-around altitude.
OR, you disconnect and shove the nose down.
Most pilots (me included) would opt for the latter.