flowering crab tree

Question

The leaves are drying up and falling off, and the bark is also drying and flaking off.

Answer 1

From the symptoms it sounds as if your crabapple has apple scab caused by the fungus Venturia inaequalis that also infects eating apples.
These links have more information.

https://www.gardeningknowhow.com/ornamental/trees/crabapple/flowering-crabapple-trees.htm
https://www.extension.umn.edu/garden/yard-garden/trees-shrubs/managing-apple-scab/