Not manually. Feeds are automatically deleted if not used for more than 90 days.
Podsync can't build a feed from just one video. You have to provide a link either to a channel, user, or playlist.
This is known issue. Unfortunately as of now I don't have any fix for this.
That happens because you're in a different region than Podsync. More details on this here. I've been working on multi-region support, fix is coming soon.
Feeds are cached for 10 minutes to reduce server loads.
No, that would require "login with your YouTube account" on Podsync. Instead you might want to create custom playlist and add there videos you want to watch.