I'll try to keep things simple. The values are for rotations around the x, y and z axes, respectively; in other words, for pitch, yaw and roll, in that order. Generally it is best to keep pitch and yaw values the same, though it is not a requirement.

<thing> = <pitch_value>, <yaw_value>, <roll_value>
steering_torque = 55000.000000, 55000.000000, 48000.000000
angular_drag = 41000.000000, 41000.000000, 35000.000000
rotation_inertia = 8400.000000, 8400.000000, 1000.000000

The maximum turning rate of the ship around a particular axis, in radians per second, is given by torque over drag. In this case, the max pitch/yaw rate of the ship is 55k/41k = 1.34 radians per second. The max roll rate is 48k/35k = 1.37 radians per second. If you prefer thinking in degrees rather than radians, the conversion is 57.3 degrees per radian, so in this case the ship would have a max pitch of 76.86 degrees per second.

The initial angular acceleration of the ship around a particular axis, in radians per second per second, is given by torque over inertia. In other words, when the ship first starts to turn from a dead stop, this is its rate of acceleration. As the ship begins to turn faster, the rate of acceleration falls off until it reaches zero when the ship is turning at its full speed. This means that initial acceleration is only a guideline that can help you determine whether your steering is "mushy" (low acceleration) or "crisp" (high acceleration). Acceleration on its own means very little, so always look at it together with the max turning rate. Lastly, Freelancer will freak out if the ratio of drag/inertia is greater than about 20 (in other words, if the ratio of initial acceleration to max turning rate is greater than 20); your ship will turn faster than expected, potentially much faster. In this case the initial pitch/yaw acceleration is 55k/8.4k = 6.55 radians/second^2. The intial roll rate is 48k/1k, or 48 radians/second^2 (very fast). Note that the roll of the ship violates the drag/inertia limit of 20, but since it is roll it doesn't matter terribly (and if the ship never rolls too far, people are not going to notice anyway).