Maybe try this,
First, before you plug it into itunes or do anything go into your itunes account, go to the Preferences in ITUNES (it is located under the top lefthand corner) of the page. Go into your backup history, you will see a listing of every the date & time of the back up & restore attempts. DELETE all of them, rest your sync history.
Clearing out all of the previous back ups might help you, it might allow you to back up and restore the phone from itunes instead of a back up of the phones settings. Then try the clock and date change, turn off/on and see where your at.
Also, are you positive your battery is the correct battery for that phone?
Also charge the phone up to 100% before doing anything.
I would almost say that you have something somewhere either unplugged but it looks like it is plugged up. Disconnect all the connectors and make sure they are plugged in fully, one might have been bumped just a little lose. Check the OTHER END of the antenna