saying things like "i know you didn't make this decision, and i'm sorry for being angry at you, but i need <elected> to understand that this is unacceptable, because <reasons>" does actually help. they're essentially doing customer service for the officials.
Very much this.
If you have the emotional bandwidth to not take out your very legitimate feelings on the person whose job it is to answer the phones, they are more likely to do what they can to work with you.
Yeah, if you're the first person they talk to after getting 100 emails overnight from the same increasingly upset person (whether or not they're on your side), giving them something annoying-but-manageable to deal with could actually hit the sweet spot.
It's sometimes more complicated -- I've called local pols' offices where the staff have been hostile out the gate. I don't know if it's because of their being exhausted by constituents calling in (and possibly being rude to them), or if they're True Believers and offended you want to talk to Daddy.