55 mph
Speed is always a factor, whether you are stopping for a school bus or not.
nope
42.4mph
It depends on where the bus is. Near a school, it's usually about 20 - 30 mph.
600
$1,000
55 MPH Source: http://www.hldi.org/externaldata/srdata/docs/sr1013.pdf
Typically, it'll be whatever the speed limit of that road is. If there are specific laws on the subject, it'll be a matter of state law, not the FMCSR. You'd need to specify a state for a more accurate answer.
80 km per hour
Where? Be more specific!
When weather and road conditions permit it.