Might the leakage be running away through the circuit that charges the battery?
I know nothing of cars - but if you have leakage with all the fuses out it does not leave many probable causes. A chaffed wire would not allow a steady 80mA drain so you can reasonably discount something like that.
Also if the charging circuit were defective the result would be a flat battery - which is what you're experiencing...
Good luck...
Peccavi
March 2011