Ultra fast fuse - are there such devices? And an IGBT question

[capt bullshot]

One thing comes to my mind now:
Does the transformer core saturate in the unloaded condition? Otherwise, I cannot imagine the high currents you describe.
For a pulse width of 2us, I don't see a measure to detect this and turn off the IGBT fast enough, so you'll have to make your circuit robust to stand this condition. Maybe some kind of air core inductor in series with the transformer primary helps to limit the current rising rate in this case.
You'll definitely have to place the snubber, free wheeling diodes and input capacitor as close as possible to the IGBT module. The length of the wires from that block to the transformer is less critical.

[BrianHG]

Looking at your circuit, have you considered a second low-side IGBT switch to discharge the transformer to 0v after the pulse?