LTC4366 killing MOSFETs
Just looking through the design procedure for this IC, you seem to have chosen an Rss that is at least a factor of 2 too high. The design calls for a current of 250µA through Rss while keeping the IC biased. 250µA through 2MΩ is higher than your supply voltage.

This IC also works in an intermittent linear regulator modality when in fault condition, so your pass-FET would be taking the brunt of the power to drop the voltage to an acceptable level. If you did not take this extra power into account (intermittent as it may be), your FETs will blow.

Attempting to drive a capacitance to ground of 3.3nF within 1ms (or even the 1nF+ capacitance of your NFETs) would require on the order of 200µA, with your 12.5MΩ supply resistor this implies a voltage drop of 2500V. The C3 charge pump is there to reduce this problem, but this only helps when pulling the gate down, not in start-up.