Hello,
For just the distance from Tokyo to Osaka, a 7 day pass would not pay off. However, if you are returning to Tokyo, or could extend your trip to Hiroshima and back to Osaka, then it would be cost effective. You are basically spending 5 days in Osaka, with one at USJ, but if you have not seen Kyoto or Nara before, you are missing the best side of Japan. Both places are well worth visiting, and offer some of Japan's best places, including in Kyoto the Kinkakuji Golden Pavilion and Fushimi Inari Shrine, and in Nara the Todaiji Great Buddha. It would be tragic if you were so nearby and missed such great places.
For Osaka, it has its good spots of course, but if you are already seeing Tokyo, a lot is simply redundant, and other places are more worthwhile.
Good luck.