Why aren't passengers seated in a seat most likely to be vacant for most of the trip. Have a computer figure this one out. For example, if I'm going from the first station on the route to the last, have computer reserve seat passengers next to me who are traveling for much shorter distances. This way, I will much less likely to be seated with a seat mate who is going the full route, as I am.
Regarding having no seat mate, why not be able to but the seat next to you. Amtrak makes the same amount of money and you get all the room you need.
Regarding the crew not enforcing the rule of headphones or no excessive noise, why don't they? There should be no excuse for them not enforcing the rules.
Sorry, but while traveling on Amtrak, the crew is assisting in the comfort of the reasonable passenger who may be traveling for two days or longer. The crew can spread out anywhere of the train.