In My area, low temps is about 30F+ only, very rare to see it went below 25F.
your winter protection seems fine, I think that those dead fig trees, They might have weaker roots system, you can wait for few more weeks, If it keeps on drying branches or rotten tips, it is bad sign of dying.
I have one test fig tree planted last fall, I dig it up 5 weeks ago and It was roots damaged by wet winter soil, fig tree do not like wet feet, I built her a raising flower bed of 12 inches, now it recover and its branches puffing up.
Young fig trees have only top layer of root system, After few more year, I think that cold hardy fig trees will form second layer of root system at deeper soil, It is much harder for cold weather to kill its 2 layer of deeper roots, and it stores more energy to re-grow new branches at spring time.