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I would just get rid of the plants that are affected. The insect that transmits the disease may not have injected the virus into all the plants.

Your pots should be fine. You might rinse them out well.

I also would not compost any affected plants. I would dispose of them in the trash.

https://www.gardeningknowhow.com/plant-problems/disease/aster-yellows-disease.htm

You do have a few things that you can expect to grow well in those conditions. These articles will help:

https://www.gardeningknowhow.com/ornamental/trees/tgen/wet-soil-trees.htm

https://www.gardeningknowhow.com/edible/fruits/fegen/fruit-trees-in-wet-conditions.htm

https://www.gardeningknowhow.com/ornamental/water-plants/wgen/water-tolerant-plants.htm

Yes, adding sphagnum peat moss can help. Here are more options:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-dries-too-fast.htm

If this is indoors, then with persistence and fungicide use and not re-using infected soils, it can be eradicated rather easily. This article will guide you on fungicide use: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

If this is outdoors, then you will have to use fungicides, in combination with constantly removing any infected growth from on and around the plant. You must keep all infected growth cut, and treat every year for the fungus. I recommend an annual treatment of DOLOMITIC LIME and WETTABLE SULFUR once or twice per year if you need a second dose. This will help condition the soil, and keep any pathogens at bay.

This article will offer some more information: https://www.gardeningknowhow.com/plant-problems/disease/root-rot-in-garden-plants.htm

Amending it with heavier elements, like compost, coco coir, and other organic matter will help.

Mulching can help, also!

Here are some articles that will help:

https://www.gardeningknowhow.com/special/organic/the-importance-of-soil-for-an-organic-garden.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/improving-garden-soil.htm

Unfortunately, your photo did not come through. I am unable to diagnose any issues with the area.

If you know that something is eating your plants, you may try a fence, cage, or net. This can help keep any creatures out of the area.

Here is an article that can help:

https://www.gardeningknowhow.com/plant-problems/pests/animals/what-animal-is-eating-my-seedlings.htm