As far as firmware and the necessary flashers .....you'll have to post it and ask around here..and get it from a fellow member ...for the time being anyway.
Concerning your problems with the device itself...
Not that you will enjoy hearing it buuuutttt...
I'd hazard that you haven't really read through the forums here on the problems with these n900's from asia ...have you?
In my humble opinion you should have come to the forums 1st ...posted some questions regarding the asian knockoffs ...and asked some folks whether it was a good idea 1st. I would have been one of the many voices trying to dissuade you from purchasing the fraudulent device.
Even the seeming best auctions on say...ebay ...you have to be cautious that you are going to get a fully functioning n900 with usb port intact....let alone the slew of other possible probs that a legit device may have over time that isn't mentioned by the seller.
But most certainly these "brand new" n900's from asia tend to be nice casing with nothing but problems inside.
Nobody else has said it yet ...and I really hate to but I think you were taken....the buy and sell here at maemo.org has genuine users with genuine devices for sale ...them you can trust...your fellow members...they won't steer you wrong....elsewhere you take your chances with sellers you don't know....who don't care about their reputation or their standing with fellow members like we do here.
My best suggestion at this point would be...grab a camera....take the back off the n900 and take some nice detailed photos...post them here...and lets see what the insides look like.....there are a few people here that know exactly what may have been tampered with or what internals have been replaced with phoney parts or parts actually made for other devices.....and then take it from there...that is the best I can suggest.