When I went to the Osaka tourney about 9 or 10 years back, my friend and I were able to get a "box" to ourselves, day-of. We didn't know about bento reservations, so we loaded up on food and drink at a nearby conbini (think 7-11 on steroids) since you can't re-enter the stadium once you leave. I agree that you should just go for the last, most pro group.
You have a very solid itin. I would consider spending one Osaka day in Kobe instead (easily reachable from Osaka or Kyoto, especially if you have a railpass)- I find Osaka to be similar to Tokyo, and Kobe has a very different "vibe." It might make sense to even base yourself either in Kyoto or Osaka for the entire Kyoto/Osaka stay, and alternate between those and Kobe to break up the Kyoto/Nara part. Reason being, you could find yourself "templed out" after 2-3 days straight, and breaking it up a bit might help appreciate them more. Depends how you like to travel.
If you are still in Japan March 27,
Himeji Castle is scheduled to fully re-open on that date. It will probably be abnormally full of local tourists that first week, but it is really worth seeing if you have a chance.
The other option to consider (mentioned above) is Hiroshima/Miyajima. I'm not a huge fan of Hiroshima city, but the A-bomb-related sites and museum are worth seeing. Google Miyajima, but it is a breathtaking site to spend at least a half-day.