Regarding [1], do you foresee this changing at some point? I'm interested in self hosting, bit have heard consistently that it is painful, so I've been waiting in the hopes that it will eventually improve.
The problem is that it is expensive. Even if you host on a cheap VPS and put your media on some object storage like Storj (~$4/TB/month), you are problably looking at a minimum of $20/month for the server. If you get for yourself, maybe your friends and stay under 50 users, fine.
If you get more than that then you'll need a beefier server, and if any of users follows lots of media-heavy accounts and does not set it up to delete old posts, your object storage will be full very quick.
I delete posts mirrored from other servers older than 90 days with a cron job. It has a command to do this.
But I am still not happy with the idea that we should be deleting data from the server just to keep it manageable. It reminds of the before Gmail where people would get 5MB quota of Yahoo Mail and would have to go around deleting stuff from their mailboxes every other month.