Hi there,
This is a bit of a classic itinerary for a 7 day JR Pass and would certianly recommend one. You can use the JR Pass for all your rail travel in the above itinerary, including Narita Airport - Tokyo and Osaka - Universal studio. The 7 day JR Pass is about the same price as a normal return ticket Tokyo - Osaka, so any additional travel is what you save.
The only thing that I am a bit worried about is your 6pm arrival. Travel in Japan stop service after midnight and you still have at least 4 hours of travel ahead of you from Narita Airport to Osaka. Therefor I would suggest spending the first night in Tokyo or Yokohama and traveling on the following morning. This is also much saver in case of a plane delay.
Hope this helps,
Daniel