Hi Mary.  Sorry to hear your having problems with your Japanese Maple tree.  White spots on leaves and curling in Summer could be a fungal infestation such as powdery mildew which is not generally threatening to the tree's viability.  To avoid, water trees in AM to allow drying during daytime, promote good airflow and avoid overhead watering and watering leaves.   https://www.canr.msu.edu/news/why_do_my_maple_leaves_have_spots  Other diseases can also cause spots on leaves. Try searching Google images "spots on Japanese Maple leaves" for possible photo comparisons to your recall.

The lack of leaf developement this Spring is more troubling.  Are there any branches with leaf bud developent?  I can't see any in the photos you provided.  Severe Winter or early Spring cold can damage buds, as can Winter Moth larvae infestation  (caterpillars are large enough to be seen.) A tree with leaf bud damage may still recover and again develope leaves later in the season.  https://extension.umaine.edu/gardening/2021/07/12/japenese-maple-tree/
https://extension.unh.edu/blog/2019/08/how-should-i-plant-care-japanese-maple

https://extension.unh.edu/blog/2019/08/how-should-i-plant-care-japanese-maple

A much more worrisome possibility is a disease destroying the vascular system of the tree such as Verticillium. This can be confirmed by analysis of a plant specimen. https://www.canr.msu.edu/pestid/  If a tree has a small amount of this disease, one can "try" to limit it by pruning out dead portions of the plant. If large portions of the plant are affected, it can't be saved.  Any plant material should be destroyed and tools should be meticulously cleaned and disinfected. The diseases is soil borne and so replacing the tree in the same spot should not be done. https://extension.psu.edu/maple-diseases

https://rtectreecare.com/blog/japanese-maple-diseases/

https://blog.davey.com/verticillium-wilt-threatens-japanese-maples/#:~:text=In%20spring%2C%20you%20might%20first,tools%20between%20pruning%20different%20trees

Finally although your tree is relatively small and only three years old consulting an arborist is always a resource to consider.  https://www.treesaregood.org/Find-an-Arborist