Cranking amps to spin an e46 should be a nominal 175 amperes.
You should be able to spin the engine if your voltage does not drop below 11.3v measured when you try to crank. To eliminate the battery as a problem, jump with another battery. Leave the battery connected for five minutes while the other car is running before you try to turn the car over.
If you still can't start the car, best to check the starter directly. Measure the voltage at the main starter terminal to engine ground. If you get 12v there, next jump the small (solenoid) terminal from the large terminal and the engine should spin. Caution; make sure the car is in neutral. If the starter won't turn, bad starter!
Let me know if you try these things and want further counsel.