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I don't think it is plum pocket. Normally, with that disease, the fruit have a pockmarked look to them.

It sounds like the plums were affected by a stone fruit exclusive fungus (which is why the apple and pear are fine). It was probably attacking the trees before the storm came, but the weakened leaves and fruit could not handle the high winds.

The fruit you are seeing now is a last ditch effort on the tree's part to produce seeds this year. They will not produce any kind of quality fruit, so it is best to remove the fruit now to prevent the tree from focusing energy on them. This will also help to redirect the energy to the leaves, which will help the trees recover faster for next year.

Treat the trees with a fungicide once this year and then get them on a schedule for treatment for next year. This article is for peaches and nectarines, but the same spray schedule applies to plums:
http://ag.udel.edu/extension/horticulture/pdf/hg/hg-22.pdf

Undiluted Round Up will help kill the roots. You will need to wound the roots (normally, people cut the suckers down and use those wounds) and then paint the undiluted Round Up on the wounds. The bigger or more wounds you paint, the better.The roots will suck the Round Up in and it will kill them. You may have to repeat the process a few times to fully kill the roots if the root system is still strong.

Less is more when it comes to pruning a Damson Plum.

All pruning should be done while the tree is dormant; early Spring or late Winter.

Shape the tree and prune away any dead or diseased material.
Remove any suckers as soon as they appear.

Most gardeners want the tree to have one central leader.
Once the tree reaches the desired height you can cut off the trunk just above the top branch. Maintain this height by pruning the top and tallest branches each year.

This can be treated with copper fungicides, which will be widely available. There are also reports of wettable sulfur being used as a treatment with some success as well.

This article will help: https://www.gardeningknowhow.com/edible/fruits/plum/treating-plum-pocket-disease.htm

The Aphids look to be still active.
These links have more information.
https://www.gardeningknowhow.com/edible/fruits/plum/control-leaf-curl-plum-aphids.htm
https://www.gardeningknowhow.com/edible/fruits/plum/plum-tree-fruit-spray.htm
https://www.gardeningknowhow.com/edible/fruits/plum/common-plum-tree-pests.htm
I'm also concerned about the green algae growing on the bark; you tree may not be getting enough sunlight and air circulation around the tree.

https://www.gardeningknowhow.com/edible/fruits/plum/growing-plum-trees.htm

This article will help you access the tree.

https://www.gardeningknowhow.com/edible/fruits/plum/plum-trees-not-fruiting.htm