If your tree is fully lignified, with no soft/green branches it should be able to withstand about 25 degrees in a container and be just fine. If it has new growth then a hard frost/light freeze can kill those branches.

If it has not grown in the past month or two and all the branches are lignified/brown I would let it experience freezing temps as much as possible to get it really good and dormant and delay putting it under the lights as long as possible. That would mean bringing it in on colder nights and putting it back out as soon as the temps are above 25 again. It will eventually be inside for long enough periods to trigger growth so when the buds swell keep it inside or they will freeze (this will be your best chance to root prune and repot also). It is a little dangerous because you might forget it outside one night or it might get frozen to the balcony or something and end up badly damaged or dead. That's what I would do though...

If it has green branches you might try skipping dormancy altogether. But remember that fig trees can be very vigorous and might end up shading your other plants, growing into the lights, getting leggy, rootbound etc. before spring.

Thanks for the reply! From what I understand the plant is actually still young enough that most of it is green and not hardened off, so perhaps I will skip the first dormancy. That will not harm it? Will I still get fruit? Can I do this every year or just one here and there?

Unfortunately once it is below the point the fig could handle the temperatures, it has to stay inside. I go to work really early, before it warms up enough to put it out, so I couldn't do the juggling inside and outside thing. It would stay inside way too long, and that likely wouldn't be good for it. However, I will definitely let it stay out there until it's for sure too cold to. It will be a good amount of dormant time, but the perfect hours will only be at night, which is what I am worried about. I am worried it will not go fully dormant if the days are above the chill zone temperatures - I have no idea if the 100 hours of chill time need to be all at once or not.

I'm okay with it getting huge, I have grow lights and enough room to keep it happy. And I've got a pruning shears just in case!

Figs can take serious amounts of abuse. You really have to put forth effort to kill them. Putting a completely green fig tree outside would likely do it in zone 3 winters.

Figs form on new growth after they get a little bit of chill time. i.e. figs form on new growth next season. You didn't say how big the fig tree is but I'm assuming it is small. I would worry about getting it healthy and put some growth on. You could attempt to get chill hours right before spring starts. I think El Nino is supposed to keep the North warmer than average.

If you are growing indoors and want max fruit each year, you will likely have to prune each year to get new growth to start again.