Air brakes are not a factor in determining whether or not a vehicle requires a CDL. As for your employer's box truck, the length doesn't matter - the weight rating does. If it has a weight rating of 26,000 lbs. or less, it won't be useful in helping you get a CDL. If it's rated at more than 26,000 lbs. GVW, it can only be used to get a Class B CDL, unless you're attaching a trailer of more than 10,000 lbs. GVW to it, in which case, you can get a Class A, but you'll have a "no tractor-trailers" restriction.
Runaway truck ramp.
Newtons law of motion comes into play here. When the brakes are applied the body of the truck will want to continue on its forward motion. The contact of the tyres with the road will try to control that forward motion.
If it's a truck which isn't considered a CMV, yes. If it is a CMV, you must have completed the written air brakes test and have done your road test in an air brake equipped vehicle. Otherwise, you'll have a restriction prohibiting you from operating an air brake equipped CMV.
On a US licence, there is no air brake endorsement - there is only a restriction for CDL drivers from operating a commercial vehicle equipped with air brakes if they don't complete the written test AND road test in a vehicle equipped with air brakes.
Find someone who'll employ you once you have a CDL, and will offer their truck for the road test. It doesn't have to be a dump truck. You could rent a 33k single axle truck from Penske with an automatic and air brakes, and, according to the DOT, it would qualify you to drive a Class 8 dump truck.
You can get a Class A CDL without air brakes - you'll just have a "no air brakes" restriction which prohibits you from operating a CMV equipped with air brakes. The vehicles you road test have to be commercial vehicles subject to FHWA regulations - recreational vehicles are exempt, so you cannot get a CDL with one.
The answer can be yes or no here, situation dependent. If you intend to operate a CMV equipped with air brakes, the answer is yes - if one does not pass the written air brakes test and perform their road test in an air brake equipped vehicle, they get a restriction on their license prohibiting them from operating commercial vehicles equipped with air brakes.
Freightliner trucks are all around great trucks to have. They run as well as any other truck on the road. It just depends on how well the truck has been taking care of as to how well the brakes and other parts will last.
The distance travelled will depend on many factors other than the mass and speed of the truck. For example, the road conditions (wet/dry), the state of the tyres and the brakes.
Take your foot off the accelerator, and slowly move back on the road. Do not jerk the wheel or apply the brakes.
Only once. In the direct-to-video movie Tiny Toon Adventures: How I Spent My Vacation, the Road Runner finally gets a taste of humiliation by getting ran over by a mail truck that "brakes for coyotes."
If you're in the US, there is no such thing as an air brake endorsement. CDL drivers receive a restriction which prohibits them from operating a commercial motor vehicle equipped with air brakes if they do not pass both the written air brakes test and do their road test in a vehicle equipped with air brakes.