I can't give a diagnosis with just this description. Brown spots or fronds turning brown could be caused by several things; watering issues, lack of humidity, pests, disease to name the most likely reasons.
These articles may help you review care.
https://www.gardeningknowhow.com/houseplants/ferns-houseplants/growing-ferns-indoors.htm
https://www.gardeningknowhow.com/houseplants/ferns-houseplants/fertilizing-indoor-ferns.htm
can you tell me what size the arborvitae fern will grow to when full grown?
Plant looks awful. The leaves seem to be eaten before they even come up. Do I spray? I’ve heard not to put anything in the crown.
This could be an insect, but it could also be fungal. A photo will help me to determine that. In the meantime, this collection of articles will help: https://www.gardeningknowhow.com/special/organic
My father has very sadly passed away and he was thrilled with this fern he bought recently. I want to take good care of it but I don’t know what type it is. I would like to know how to take care of it over the winter. Could it be a woodfern?
This certainly looks like a wood fern. This article has a nice photo for you to compare and lots of info on how to care for the fern:
https://www.gardeningknowhow.com/ornamental/foliage/wood-ferns/wood-ferns-in-the-garden.htm
I've grown in containers and in the ground around my home; cut them down and cover them with mulch for the winter, or will they be just fine?Are they evergreen or the perennial?
They are hardy to zone 4 so they should be fine with just some mulch around them. The ferns will die back and return in spring. They are perennial but not evergreen. Some evergreen ferns for your zone are Christmas fern, Autumn fern 'Brilliance,' and Japanese tassel fern.
https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-5/growing-ferns-in-zone-5.htm
Does the kangaroo fern need to be placed by a window for bright sun light or in a room with little sunlight?
They like bright, but indirect light. If you do not have a bright room, then a small fluorescent fixture will suffice. They don't really need direct light.
This article will help: https://www.gardeningknowhow.com/houseplants/kangaroo-paw-fern/growing-kangaroo-foot-ferns.htm
There are barren sections that run along the fronds. I’m in zone 9 (Seal Beach, California). The ferns are in hanging pots under eaves. What causes this?
Ferns are relatively carefree, and there are only a handful of things that can cause this.
Temperature can cause this, though, you are well within most ferns native regions
Lack of humidity can be a cause. They prefer a humid environment. Dry air will dry out the plant.
Lack of water is a very common cause. If the soil is allowed to dry out completely, this will be an expected behavior.
The most likely cause, is too much light. They can't handle full sun, so if the plant is allowed to creep into it at all, this can cause the issue that you are seeing.
Usually,it is a combination of one or more causes. You can remove any dead growth, leaving living growth alone. Giving it proper care, balancing its needs, will ensure a healthy plant.
This article will help you with their care: https://www.gardeningknowhow.com/ornamental/foliage/ferns/brown-tips-on-garden-ferns.htm