Your form on good mornings play an important role on how much weight you can do. Try to use as little leg drive as possible, what I mean is try not to squat the weight up after you have bent over, this might be why you can do a good morning with about the same weight as you squat. For your second exercise, immediately after the ME exercise, do either 3 sets of dimmel (not sure I spelled this right) deadlifts, reverse band deadlifts (w/minis), or high pulls. For your 3rd exercise ham/glute raise or reverse hypers will suffice. The are other exercises you could do instead of what I have listed. Although, I believe these exercise should be the core of your ME Day. Box squats are okay to do for your ME exercise once in awhile, but you should use a low box (~3-4 inches below parallel) and do the squat as a front squat or Mante Ray squat, just do something slightly different from your speed squats. These are just some ideas, hope they help.