Cytospora on trunk?
I have a Higan Weeping Cherry in my yard, planted about 16 years ago. Several years ago it developed a split on the trunk that looked like it was behind the bark, and last summer the bark pulled away. There is also a glob of dark colored sap on the opposite side of the trunk. There does not appear to be any insect damage. It has always bloomed beautifully and looked healthy, covered in leaves. Now there are several dead branches and half as many blooms. I've looked into what it could be online and am guessing it has Cytospora. It is not in an area where it could have been damaged by anything, it's surrounded by perennials, no grass. Is there anything that can be done?
You probably have multiple things going on here, and this is pretty common on ornamental fruit trees like Higan cherries. The blooming fruit trees are not very long-lived; no where close to shade trees.
It wouldn't be uncommon to have canker diseases, and the gummosis that you see (hardened sap) is indicative of either a wound, but more likely a borer. There is not much to do about them.
It also looks like- in your first photo on the right at ground level. that you may have a girdling root which can stress/kill a tree over time.
Here is a publication that can help you see all the problems they often have towards the end of their life: https://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG93_IPM_Series_Orn...
You probably have several more seasons of beauty ahead of you. This happens slowly over time. Simply prune out any dead wood, and keep it well watered should we enter any period of drought.