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This sounds like a big problem. I will have to recommend a few things.

First, you should apply dolomitic lime to control the pH, as it sounds like it is slowly getting off kilter.

Second, You will have to find something to control the insect problem. There are many things that can do this organically. I use neem oil for many insect pests, personally.

These articles will help you: https://www.gardeningknowhow.com/special/organic/

It may help, but it is likely that it will not respond to the treatment. You can take a clean, sharp knife and scrape the are. This might help. Here is an article for the care of yuccas: https://www.gardeningknowhow.com/ornamental/foliage/yucca/caring-for-and-landscaping-with-yuccas-outdoors.htm

You can remove some of the lower browning leaves. This could be an infection starting. Apply, both, dolomitic lime and wettable sulfur to the area, and this can help it to recover.

This is called wound dressing, and there's really no need for it. Plants form natural calluses over wounds, and coating them in rubber or tar just prevents that process. This article is about trees, but the principle still holds if you want to read more about it:
https://www.gardeningknowhow.com/ornamental/trees/tgen/wound-dressing-on-trees.htm
Yuccas are tough and used to pruning. As long as your plant gets lots of light while it's recovering, it should be fine on its own. You can read more about yucca pruning here:
https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plants-care-and-pruning-tips-for-pruning-a-yucca.htm

It seems that your entire state is within the range for any yucca to grow just fine. You have the ability to pick, just about, any to grow.

It will not regrow leaves from the bottom of the plant.
You can however prune for height.
This article will help you.

https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plants-care-and-pruning-tips-for-pruning-a-yucca.htm