Q.Dogwood Tree Question
I planted a healthy dogwood tree from a local nursery 3 years ago (spring) and the first summer was very rough – very hot and little rain. I watered my new dogwood according to the suggestions of the nursery (one very large bucket with small holes in the bottom once/week). My intuition told me that this was not enough water but I adhered to the nursery’s suggestion anyway.
That first year, the tree lost a lot of leaves and has not really bounced back very well. Since that time, it has gotten plenty of water; however, I still am concerned that the first summer it really needed more water, despite the nursery’s suggestion. Right now, I have about 1/4-1/3 of the tree blooming and the remainder of the tree just looks like dead branches. Does anyone have a suggestion? Should I prune off all of these dead-looking branches, fertilize, replace the tree, etc.? I would greatly appreciate any recommendations. Thank you.

I feel your pain! Your correct that your tree most likely not get itself established enough that first stressful, hot season. Daily watering would have been my recommendation as you do not want the roots to dry out between watering on a new tree.
You can go ahead and trim away the dead material, but I would wait until Summer, as the sap is not flowing in the heat of summer.
Here is a great article about the care of Dogwood.
https://www.gardeningknowhow.com/ornamental/trees/dogwood/caring-dogwood-trees.htm