1. BTL LO means that the respective bottle A or B on the wing (on the engine with RR) is emptied
2. of course everything that helps but keep in mind that with power changes you still have to control more/less rudder
3. pulling is arming the squibs on the fire bottles and more important closing the engine fuel and pylon valves so no more fuel enters the engine and strut,
turning L or R empties the respective fire bottle
4. autothrottle and autopilot still work beautifully with one engine shut down on a 744, you can still do a low vis autoland in this config.
Have fun