The tree doesn't look good. The pruning of the branches probably had nothing to do with the problem. Wounds from pruning should be sealed to prevent bugs or other pathogens from having easy entrance to your tree. This however could be from your observation of a "rainy summer". Poor draining soil at the sight of the tree could drown the roots causing root rot.
This tree is also susceptible to Verticillium Wilt! A fungi that shows the symptoms you describe. Wet weather is like steroids to this fungus. Unfortunately there is no treatment for this disease. Some trees recovery the next growing season others hang on for a few years before they die.
I could't make a positive id of your problem. Probably not much you can do. I would not pump water, chemicals or fertilizers on the plant, this would do more harm than good.. You will have to see if the tree can work it way out of this problem.
Trees are very resilient and have survived despite our "help". The amur is a very nice maple especially in the fall.Good luck with yours

Thanks so much for your insight, my soil has some clay content. The tree looks worse every day, especially at the top. attached is a photo of an affected leaf that shows how the wilt spreads. If it dies I am thinking to replace with an Acer Griseum but would it suffer the same fate or is it more resistant?