No, this is not recommended for your stated application.
I used it on my Son's 1967 Ford Falcon Futura's hood 3 years ago and it's still in excellent shape. I used a heavier foam backed product on my diesel ramp truck to deaden noise, as this really only insulates against the elements, not noise. It probably does to an extent, but not on a loud diesel.
rub it down with an old burlap bag. the coarse material will remove a lot of the mess.
I don't see why not. It is sticky. But they do sell garage door insulation kits that have thicker insulating value.
I would say yes. It is sticky on one side and you would just cut to fit as required.
where would you put it...? If you restrict air flow, it would burn out the motor...and if you just put it around it I don't see it doing much good, unless your trying to keep cold from attic out of your kitchen. since most of the sound is going to come from the air movement and the sound of the motor, im not sure this is the correct product but others may have a different opinion, I love the product,...good product and not over priced.
It depends on the size of the vent. The usual answer is YES
It sounds to me like this would be the perfect choice for the sun tubes. I was just about to install two myself, I never thought of them getting hot. The self stick is very helpful when trying to get the insulation to stay without having an extra set of hands.