There should be no oil leak between exhaust and turbo, only if turbo is leaking into exhaust housing and if it is do not use the car till its fixed. Whip the turbo off and check for play in the shaft, you losing oil? Any blue smoke?
Sounds like a catalouge of errors going on, out of the few T series focus's i have seen now they all look like they had been hacked about a bit under the bonnet. Sounds to me like your left fixing the previous owners bodges?
I would literally start from scratch and make sure EVERYthing is working correctly/leak free