Adding friends in mousetopia is easy, in the main Lounge, just click on a username and then click Add Friend.
Ok I think we finally got the rank thing fixed - if you change your default park to WDW, it moves your points to WDW and you are ranked among WDW users. Or you can leave your default as DL and in the WDW Lounge it shows your rank in DL. I recommend you set your default to whatever park you visit the most. Let me know how it is working for you, thanks!