Hi Genedaniels,
I often compare fig trees to tomato plants .
If the buds are just greening, you would be safe with lows above 5°C / 40°F - So no leaf, no stem growth.
If you have big softie leaves and green stem growth , you would be safe above 15°C/ 59°F .
If you have hardened leaves, you would be safe with lows above 10°C / 50 °F.
You can play with the limits, but you might see burned edges on the leaves .
Of course throwing a plastic sheet - for making a cheap greenhouse - over the pots will help them - but definitively I wouldn't attempt to go under 2°C / 36°F .
Now where are those 4 stakes ? :)