I finally got caught up on projects and had some time today to get back to the Quick Hitch. I think I have it working with my blade. The problem seemed to be that the two plates on the quick hitch where the top hook mounts were spread too far apart. To make matters worse the side plates appeared to be flared slightly, making the problem worse. I took a two pronged approach to solving the problem. I put two washers on either side of my rear blade which opened up the hook channel about 1/8". I also bent the two hook mounting plates in a bit on the quick hitch and took out some of the flare. The top hook now fits better in the channel.
I mounted and dismounted the blade several times and it seems to be working much better. I'm not sure if my top link bushing is still correct. It still has a fair amount of slop in the hook. I'm currently using a Cat2-Cat1 bushing from Tractor Supply (#268446).
Below are some photos to show how things look after my modifications. Thanks again to everyone on this forum for your help.
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