That sounds very interesting. From what I have learned, here is how the bomb works:
When the bomb is being armed, and you run out of the circle with the bomb still in your hand, the arm time will go down twice as fast as it would go up in the circle. However, if you get killed while arming, and the bomb flies OUT of the circle, the arm time will STILL be on it, however when you or a teammate pick it up, it will go down TWICE as fast as it would UNTIL you get back in the circle.
Its a easy concept but hard to put into words. For example, if an assault game has 5 second arm time, and your teammate arms it for 4 seconds, then gets blown up by a rocket launcher, and the bomb flies a little bit out of the circle. If you get to the bomb, pick it up, and take ONE second to get back in the circle, it will probably be down TWO seconds. This will leave the bomb with 2 seconds still on it, making it so you only have to arm it 3 more seconds.
The big problem is that if the bomb is more than 2 seconds away from the circle, your arm time is totally gone.
As far as disarming it is concerned... there is no way to prevent it. The only thing you can do is prevent it from being contested and make it return.
Hope this is all correct / makes sense
