So sorry to see your tree is not happy.  Your images are excellent and helpful.  The branches have a fungal disease that is causing the cracking and oozing of the bark.  The tiny maggots are likely plum curculio.  Both of these issues are common and require preventative action.  At this point, you should collect and destroy all affected fruits.  Do not leave them on the ground since the insect completes its life cycle on the ground.  Then you will need to try to prune out the branches with the fungal disease and burn them.  Lastly, you will need to apply fungicide and insecticide now and also next spring at bud swell.  Do not apply insecticides during flowering, though, to protect pollinating bees.

OMG thank you so much for your very comprehensive reply. It’s amazingly helpful! Can o ask if you have a suggestion of fungicide and pesticide? I’m out of my depth on that front. 
again thank you so much  

Barbara

My pesticide recommendations are limited to the state of Florida, so you will need to double-check to make sure these products are available and legal in Virginia.  Please refer to this complete guide that we use for plum horticulture in Florida, and then scroll down to the areas for insect and disease management (both of these will describe the issues and then link to current pest management documents produced by our university specialists): https://edis.ifas.ufl.edu/hs250.

Be well,

Carrie

I hope it helps! 

be well,

Carrie