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This is a common sign or either aphids or scale bugs. You can spray the plant with Neem oil, when it is not in bright light.

This collection of articles will give you more information on crafting your own insect remedies, along with many other helpful tips: https://www.gardeningknowhow.com/special/organic/

Yes, this sounds like a good plan for your Eugenia. Just make sure to dig it up and bring it indoors before temperatures fall down to 25 F. You'll probably need to repot it every 3 years or so. There's a chance it may someday get too big to lift in and out of the ground, but for now this system should work well.
Here's some more information on Eugenia growing in and out of containers:
https://www.gardeningknowhow.com/ornamental/shrubs/eugenia/growing-eugenia-plants.htm

You will need to build or purchase a frame and cover it on sub-freezing nights/days with clear plastic.

https://www.google.com/search?q=plant+frost+protection+frame&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwi7kZCwyMDcAhUZdysKHY6hBOYQsAR6BAgDEAE&biw=1280&bih=626

There are many species of these. Some are shrub forms, and some are tree forms. It looks like what you have is a tree form. They can tolerate quite a bit of pruning, and need it to stay shorter. The type that you have may not be a compact growing shrub, and may be difficult to force into a compact shape.

It can be even more difficult to grow these in container. They can be slightly picky about the soil type, and especially picky about light. They require partial shade, so if that area gets too much sun, then this can prevent proper growth as well.

This article will help with the care of these: https://www.gardeningknowhow.com/ornamental/shrubs/eugenia/growing-eugenia-plants.htm

Those are a type of insect known as "scale". These are very aggressive, and develop a shell to protect it from pesticides. You will have to scrape off as many as you can and then treat with something such as neem oil, or other insecticides.

This article will help: https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm

I reviewed the lists from the SPCA and found no reference to toxicity of Eugenia spp for dogs, cats or horses.
https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/e?&

But there are over 1000 species in the genus Eugenia, so it would be best if you were more specific in your identification of the tree and type of animal that you are concerned about.

I have eaten fruit of Eugenia myrtifolia, Australian Brush Cherry many times. It's sour and I wouldn't want to eat more than a few, but I experienced no sickness. If an animal were to gorge on them and eat the hard seed core, then it may develop problems that aren't necessarily toxicity.

It's always best to check with a local vet or animal welfare organization in your area.