Not sure if my math is correct, but this is my first stab at calculating the theoretical failure to intercept a missile with the launch of 8 interceptors.
(1.00 - 0.61)8 = 0.0005352009 = 0.05%
Which translates to a success rate of 99.95%
I just did that for fun. I do not claim to be Albert Einstein.
Then you run out of missiles very quickly which is what happened in Israel. Their systems have shown they can’t deal with overwhelming missiles coming in, no system can. We have no capability to handle thousands of incoming missiles.
Let’s see by your estimate then with 14,000 incoming Russian Missiles we would need approximately 11,200,000 missiles to shoot all of them down. Where would we get these from and how long to make them. Better off building a Death Star.