I feel the majority of the advice here is good. I also agree you are in no mind set for
PUA yet, focus on the more important things such as working on your self confidence, social skills and building friendships with people. It seems you are regretful of your youth in not pursuing sprinting. However know this; having one limiting factor that you accept as your identity is a recipe for depression and low self esteem. It is evident even in incredibly succesful athletes, take George Best as a good example of many. Learn that people can and will love you regardless, provided you work on yourself and know you are worthy of their respect. Most people in life who are doubted, doubt themselves.