You are making it too complicated.
First off, the primary voltage does not change. It stays at the same voltage it was at prior to firing. The part you are not picking up on is that the only change in your circuit is the ground is being removed. You have a voltage (let's say 14 volts) at the primary + side of the coil and a ground on the - side of the coil. Your circuit at this point is completed. Electrons are flowing from the + side of the electrical system/battery to the - side of the electrical system/battery. Electrons will always take the path of least resistance and that's what they are doing now. This is where the term "short circuit" comes from.
As you open the ground, you've got positive electrons looking for a way to continue over to the - side of the system/battery. They find a path through the secondary windings of the coil. Since there is also a magnetic field present, they build up in voltage until enough energy is created to jump the gap across the spark plug electrodes. The energy created in the magnetic field and secondary windings could also be looked at as a capacitor. Once the spark plug fires, the rush of electrons under high voltage jumps across the gap. But since the secondary windings of the coil have a high resistance to current flow, once the built up energy is released, there is not enough current flow available through the secondary winding to continue to fire the spark, so it dies out.
When looking at CDI (capacitive discharge ignition) systems there are basically two designs out there, which are ussually combined into one unit. One of which uses capacitors to build up and store additional engergy to help push additional current flow through the ignition coil. If I remember correctly, my AEM C2DI can raise the primary voltage as high as 540 volts prior to firing the coil. This additional voltage "push" helps maintain enough current flow through the secondary windings to help jump the spark across the plug gap and maintain it for longer. The second design type uses mulitple spark technology to allow the ignition coil time to "saturate" the secondary windings with electrons and fire again as needed, ussually several times for the same combustion cycle. As rpm goes up, the number of mulitple sparks goes down. My AEM C2DI does this also.
For every combustion cycle this get repeated.
So it really is quite simple.
