On the last picture down at the bottom left corner, do you see how the color of the leaf is mottled, light green and dark green. That is a sign of a nutrient deficiency.
You planted it 4 inches ABOVE THE GRAFT? I made a mistake. I thought that enlargement of the trunk was the graft point. If it is planted 4 inches above the graft it is planted WAY, WAY too deep. Google root flare and google root flare grafted trees to understand better of what Is going on. If the graft is buried I am afraid you will have to dig up the tree and plant it in a hole of the proper depth, and, do it ASAP. Those two bugs look like june bugs. Very harmful, especially to your lawn as the grubs eat the roots of the grass. There really isn't much you can use to get rid of these things although spinosad is of some help. To protect your lawn use beneficial nematodes. Now for the fertilizing. That fertilizer you used is a chemical fertilizer and is much more suited for your lawn than it is for any tree. Those spikes you referred to are about useless. You need to fertilize this young tree at last 3 times per year, preferably 4 times. You should use a good GRANULAR organic fertilizer. I don't know what is available there but Fox Farms, Dr Earth, Medina, Espoma, among others are all excellent fertilizers. Stay away from any Scotts or Miracle Grow products. Make sure the bag has OMRI on it