0.01 Ampere from a good 65 Ah battery will last for 6500 hours, that’s about a year. Are you trickle charging the battery with the car circuit connected? The leakage may be bigger than the trickle charger can supply and then battery voltage will drop and gauges etc won’t work but also Amps will drop because there’s no voltage left to drive it. What is now the voltage across the battery terminals?
You might want to disconnect the car from battery (neg lead is sufficient), charge the battery until it is full, confirm it has >12 Volts across the terminals, then measure leakage current from battery neg terminal to car neg terminal. If the battery by itself doesn’t reach >12 Volts when fully charged it is (partially-) dead.
Note the trickle charger needs voltage across the terminals in order to start charging. If the battery has <8 Volts you could use another good battery to force charge it some and then complete charge with the trickle charger.