Congrates to Southern Cal Cush who won his age group 50-54 5k Nat at 54 nice job!
Mike, signup for the 8,15,mile and 3k ... then pick one;)
Since it hurts your hammy when you sprint , I would go long. I am working on recruiting for the 3000 . Counter intuitively running clockwise helped me on the curves when my left upper hs was hurting on the hard stuff. But the clue is pain occurs when you get up on your toes. WAG more of a nerve impingement than muscle tendon issue?
Gotta suggest you try 10 percent grade regular treadmill power off. Think of it as sled work or pushing a car. 2 minutes forwards and 1 minute backwards. Not hard even slow steady pushing that belt.
Another thing that has helped me is Ben the knees over toes guy amazing stuff.