The speed of sound is actually a moving feast, depending on air pressure, temperature etc. As to insurance, most insurance policies for household and car have a war/hostilities exclusion clause, which mentions damage through sonic boom.
For practical purposes, at the levels where aircraft operate the only real factor is temperature. Square root of the ambient temperature in Kelvin multiplied by 38.945 will give you local speed of sound in knots.
As for compensation, airlines here would get claims from farmers re ruined crops from all over the country any time it was reported an aircraft returned to land, whether dumping fuel or not. Eventually an area was set aside for dumping fuel to avoid spurious claims from farmers out in the gramadoelas trying to cash in.
As it is, the concentration of any fuel dumped by the time it reached the ground would have been microscopic and of no consequence, taking into account flow rate, speed and altitude. There's a good reason crop sprayers fly under power lines.
As for chemtrails at FL 350... Pshaw!