HIP4082 input & bootstrap problem
You're right to be concerned with how the bootstrap capacitor will be charged at low frequency.  Bootstrap N-channel gate drivers (like HIP4082) have a known drawback that they can't operate at 100% duty cycle, because the bootstrap capacitor discharges over time.  Similar thing can happen if the frequency is very low.

You could use a large bootstrap capacitor.  If your application allows it, you could short off-periods when the gate is low - just to recharge the bootstrap capacitor.

I have ran a bootstrap circuit** at 60Hz.  The capacitor discharge wasn't a concern.  i would imagine that you could use a bootstrap gate driver at 1Hz.

**  That was a bootstrap gate driver made with discrete components.  It wasn't a HIP4082.  YMMV.

By the way, this app note can come handy.