Not sure about a decrease, but you can easily get it fully refunded if they fuck up. I tip really well because I used to be a food courier myself. Every few months some idiot delivers my pizza upside down or leaves my order outside my building and I get my tip refunded with ease. I have no idea if that money is refunded from the dasher’s pay though.
Yes. I still use my classic regularly. 20 000+ songs on it without ever being connected to itunes. Rhythmbox for linux works great when I want to switch things up. Winamp did the job back when I was still using windows. Maybe you were forced to use itunes briefly back when the ipod was first released, but it didn’t take long for other programmers to figure out how to make their software compatible.