Hi there!

So here's some background. About a month ago, I got a 6 ft Ficus Benjamina from a retired lady. She travelled often and when she would leave she would turn her heat way down in the house. This resulted in her ficus losing 1/2 it's leaves. So she gave it to me - in this state - to care for and hopefully revive.
The plant is next to a SW facing window and receives 1-2 hours of direct light and approx 6-8 hrs of indirect (I live in northern Alberta, Canada so light is still sparse and there's still snow on the ground). I've fertilized once with liquid fertilizer. Water approx weekly enough water to drain out the bottom. It never sits in water.

Here is my issue - The tips of the bare branches are green and there are tiny shoots of new growth forming. But once I see them, a few days later they shrivel and turn black. I have then been cutting this off - only the black - as there are new growth shoots further down the branch. Why is this happening? The other half of the tree drops maybe a leaf a day (green healthy leaves)and seems to be ok other than new growth turns black as well. The leaves it has are all green - no yellow - maybe the odd brown tipped leaf. Please see pictures.

Why are the tips and new growth turning black and dying? Should I just cut off all the bare branches and start new? Would the tree be able to survive such a severe haircut?

Any help would be appreciated. I'd love to restore this tree to its former glory!

Your Ficus tree, where it is located in the photo, is not getting nearly enough light, especially given your northern latitude. Ficus trees are light-lovers and do best with maximum indoor light. Move your tree out of the corner where the walls are blocking most of the light and place right in front of the window and make sure the window is completely uncovered during the daylight hours. Providing adequate light is the most important factor and nothing else you do will matter if the light is not strong enough.

In poor light, the plant does not grow very much so it uses less water and nutrients. As recommended by Daisy, stop fertilizing. Allow the top inch of soil to dry before watering thoroughly. As the light improves and growth recovers, it will need water more frequently.

Any brittle stems should be removed entirely, as they are dead. Any of the remaining live stems can be pruned back to any length and you will get new foliage emerging just below where you make the pruning cuts. Because Ficus trees respond very well to pruning and because your tree is so sparse, I would prune back all of the stems by one-third to one-half. That would leave you temporarily with a naked tree, but as the light improves and new growth comes in, you will have a much more attractive tree without bare, leggy stems. I know that seems extreme, but in good light, Ficus trees are fast growers and recover quickly.