That sucks, I'm in the same situation. Wanting to promote my account without a console.
<======= About my gamerscore, I have a competitor's console so I game there but I also have a Windows 8 PC and I want to use my XBL account on there. I would also like to change the MS account associated with my XBL account but you can't do it without a console either. :/ Man! the competitor's account management is so much more useful online without a console, you can do everything.