Managing your social graph
Something akin to a following list could help this. Or a modified version of OPML subscription lists could work. They just need to be opened up a tad.
Some are working on the idea of an open microsub spec which could be transformative as well: https://indieweb.org/Microsub-spec
There are actually three problems to solve, reading, which is relatively easy, posting, which is harder, and social graph management, which is quite complex
I might submit that posting is possibly the easiest of the three and that the reader problem is the most difficult. This is based on the tremendous number of platforms and CMSs on which one can post, but the dearth of feed readers in existence.
How do we decentralize the web without so decentralizing our own social presence that it becomes unmanageable?
You've already got a huge headstart in doing this with your own website. Why bother to have thousands of accounts when you could have one? Then, as you suggest, password protected RSS feeds out to others could allow you to control which audiences get to see which content on your own site.
It looks as if Withknown has made some progress in this area with syndication plugins.
WordPress has lots of ways to syndicate content too.
Subscribing to my personal timeline(s) with my favorite RSS reader would bring everything together,
I've written some thoughts about how feed readers could continue to evolve for the open web here: http://boffosocko.com/2017/06/09/how-feed-readers-can-grow-market-share-and-take-over-social-media/
listed items chronologically independent of source
Having a variety of ways to chop and dice up content are really required. We need more means of filtering content, not less.