Yup the VIX is annualized. Your calculations look correct as far as my understanding goes. To add:
VIX/16 = daily 1 SD expected moves
VIX/√52 = weekly 1 SD expected moves
VIX/√12 = monthly 1 SD expected moves
You could hedge out with a USDCHF positions to mitigate any upside risk in your GBPUSD position.
GBPUSD is approaching the 200 sma on the 4hr so there is a potential bounce incoming if you can hold on.