i have the exact same cooler and installed it on both a gigabyte 770 and 970 mobo, you need to use a good amount of pressure. Make sure the screws are out far enough and then push down pretty hard.
I had the exact same problem and it was driving me mad so I installed the stock CPU fan/cooler that came with my amd 8-core 8150 (motherboard - Gigabyte 990 FXA-UD3. So the opposite side that sticks up can be forced down and it doesnt bow? I feel like either the standoffs need to be taller or it's simply in incompatibility issue. In every video I watched the retention plate screws touched the standoffs when they put the tower down on the CPU and from there they easily hand tightened all four at least a couple threads.