Yes, most devices recommend you to lower the brightness to lower power consumption. On my LifeBook I use full brightness, but i learned that just after 40 minutes it discharges. When I lower the brightness as recommended it last almost two, or even three times, as long. So I also recommend lowering the brightness.
On most devices that have adjustable brightness, the dimmer you make it, the longer the battery lasts, so yes, it should save the battery.
Yes , well atleast it does mine other computers could be diffrent .
Yeah, it usually does unless you have some un-ordinary computer. :)
what kinda laptop do you have?