Looks like Firefox Live Bookmarking doesn't like Apple Weblog URI's using "feed://" instead of "http://" (tested Mac version 1.0.4 and Windows 1.0.6). My Sage extension doesn't like feed:// either. However, once I manually changed the links to use
http:// instead, both the Live Bookmarks and the Sage extension loaded the feed. Clunky but you can make it work.
As for RSS subscription options, you might want to consider using a reader external to your web broswer. In my limited testing, Thunderbird does a decent job. There are many others, free and not so free. You can force Firefox's Autodiscovery of RSS feeds to send the feeds to an external reader by installing Feed Your Reader. (Note, I have not installed it ... yet)
Or skip the external application altogether and subscribe to your RSS feeds at a website like Bloglines.
HTH!