I don't know what Google was thinking with the Facebook widget. It is unusable! 1) It does not honor the people I choose to "hide" in Facebook. I have friended a couple people who post some of the most asinine comments, so I hid them in the web app, but the widget still shows their posts. 2) When I tap the right button to go to the next post, it jumps back to the first post within seconds.
I think with the old posts it might be due to the comments. I think each time a new comment is added to a post in Facebook, the Facebook app / widget both see this as a reason to move the post back to the top of the list. But that's just a theory.
Sorry I can't offer any other alternatives. I have no idea why nobody has developed a decent Facebook widget - maybe the Facebook API doesn't provide the necessary functionality for developers. Anyway, I just wanted to pile on and vent, as well as tell you you are not alone.