Einmal ist keinmal
You'll Never Walk Alone
There is no way to kill the FSP other than corruption (unlike other companions).
It is easy to slip away from a big noisy army. Only the flying Nazgul may find them.
Any army in the same region as the "last known position" of the FSP will also grant a hunt reroll (the same way one or more Nazgul does). I suppose you're right about the cards though. The event cards usually require having a Nazgul in the region.