3 issues in a traffic stop

My son was stopped for speeding while another vehicle was
harassing him (following, passing, slowing down) the trusty
Texas DPS trooper stopped my son for speeding, watched the
other vehicle leave, then proceeded to give my son a breathalizer which he passed,(he had had nothing to drink!),
then he insisted my son take another breathalizer which he
also passed. Then the office called in to town for the drug
dogs to come sniff the vehicle, they found nothing, there
was no probable cause, my son was given a speeding ticket, after being detained for at least an hour and a half. Is this illegal detainment...harassment? Does he have to explain his presence on that road to the officer? If two vehicles were that close together is it possible that if there was a radar gun involved that it measured the speed of the other vehicle? Are radar guns effective in the pitch black (on a country road with no lights)?
Morally, should we just let this go or since the police in this area have a reputation for harassment what are our chances of getting justice? Thank you for any advice, Suba

I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.

Morally, let it go. But this is why I don't trust police officers. Basically, the officer has a right to stop your son and test him. One hour detainment is not unreasonable.

I agree it may have been unfair, but don't concentrate on the negative. Let it go.