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Fruit trees are very susceptible to frost cracks or bark splitting due to the fact that they have thin bark. These are cause by drastic temperature fluctuations.

The fig fruit is actually the flower of the tree with both the male and female parts. So no, you do not need two trees in order to get fruit.

This article should help: https://www.gardeningknowhow.com/edible/fruits/figs/fig-drop.htm

Are you sure it is a Celeste? To be honest, it almost sounds like the figs are not properly pollinated, which would not be a problem with the Celeste. The other possibility is that the tree is not quite mature enough to hold onto its fruit well. The older a tree gets, teh better it is at producing fruit. If you have not read this, this article will help as well:
https://www.gardeningknowhow.com/edible/fruits/figs/fig-drop.htm

Celeste figs are considered among the more hardy varieties, so it might survive. The best thing to do is wait and see. This article will give you some information: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm

Generally, these plants draw all the nutrients they require from the soil; therefore, regular fertilizing of figs is not usually necessary except for potted trees or those growing in poor soil. Fig fertilization also depends on whether your plant is young or mature.
For a young tree, fertilize in late winter or early spring. For mature fig trees, fertilize monthly from early spring until July. Use one-third pound of 10-10-10 per foot of plant height each time. A mature plant should develop only one foot of new growth each year.

Yellow leaves are normally a sign of stress, perhaps in this case from the abundance of fruit. They normally require additional watering during fruiting so if it's not getting enough, then you may need to give the tree more water, especially if it's been warm lately.