Traveling Osaka to Shanghai for 68 hour visit before exiting to Tokyo and US. Am I eligible for 72 h

Unfortunately not because your itinerary is not a transit. The first and the simplest rule of visa free transit states: Only the immediate points before and after a Chinese destination matter and they have to be in different countries. As you can see, your immediate points are in one country - Japan. To be eligible you will have to insert some other country or eligible territory between Osaka and Shanghai or Shanghai and Tokyo to be eligible for 144 hour visa free transit in Shanghai.