Sounds like you've done a lot to try to fix it. Although T-Mobile does not guarantee full functionality of non T-Mobile phones, we should be able to get it working. Just a few questions:
- Did you also try downloading the Facebook app from the Blackberry APP World?
- Are you using Wi-Fi or going through the T-Mobile network? (You may run into trouble setting apps over Wi-Fi)
- Is your software up to date? (Having out of date software can definitely cause issues with downloaded apps.)
You may also consider contacting the manufacturer for live support.
Hope this helps!