as Don advised against the pruning, I know from Yama san the same and that the cherries in Japan are different varieties than our cherries. But even the fruit bearing cherries, as I remember,are huge trees, not pruned.
Lots of ch.trees have some fungi or virus infection, we used a kind of spray early in the spring, before the leaves came out. The infected branches turned black with dry leaves. Now , after 2 years spraying, no problem. But our tree was damaged, once a soil delivey truck backed in and broke one huge branch. Since the tree is lopsided.
Even in this cold spring, the tree bloomed for my birth's day, end of April.