1. Ajit Pai was nominated by Obama, and had served his 5 year term as FCC chair. Trump renominated him.
2. Who knows what's really behind it, but officially, the idea is to charge companies like NetFlix more if they don't want their customers to lag. Supposedly they plan to use the money to expand the backbone, which is a good thing. Probably will affect some high bandwidth online games, but why shouldn't it? No one seems to mind if delivery services charge more to haul heavy packages, or to be sure the package will be delivered by 10AM tomorrow.
3. Content should be unaffected, it's focusing on throughput. Even so, stuff is already filtered by content. Look at the demonetization of SOME channels on youtube based on politics, content filters on Facebook, Google admitting to prioritizing pages with the "correct" political slant, etc. To the extent Net Neutrality exists, it's not accomplishing what you say you want anyway.
Personally, I don''t see much of a downside. Lots of sites have become bloated with high-bandwidth fluff, 90% of which I don't want, let alone need. I'd rather have the option to have a lower-bandwidth page, ads and all, then click on whatever things I'm interested in rather than video popups of the Kardashians until I close the page, sometimes even close the browser. If sites have to start paying money to send me video updates on which stars are suffering from ED, I probably won't have to listen to it as much.