Yeah I know what you are talking about.
One that large scroll, when you open it up, all the letters make up the shape of a key. Whenever a seal jutsu or summoning jutsu takes place, it usually has lettering that spreads out... or condenses. Think of Itachi helping Sasuke with the curse seal. Or Tenten's weapon scrolls...
The key according to Jiraiya and the Frog is to either open or close the seal on Naruto. The seal naturally opens slowly overtime and the more he uses the 9-Tails. Jiraiya was holding onto the key because it Naruto is in possession of it, and is unable to control the 9-Tails... noone will be able to turn the key and "re-lock" it. Jiraiya was warned about giving the key directly to Naruto, upon his death, for this reason... In fact, the huge scar on Jiraiya's chest was from him experimenting with opening the seal "just a crack"
Hope that helps... I do know that Naruto is supposed to have inherited the key. But he hasn't gotten it yet.
The scroll with the frog is the key that can make the seal on Naruto stronger so it doesnt open or it can open the seal too. The Frog tell Jman that he couldnt believe that Jman talked him into cracking the seal just a bit. I think this means that when Jman took Naruto to train for 2 years, Jman told the frog to crack the seal a bit to see if Naruto can handle it but obviously he couldnt cuz Naruto transformed to the 4 tails and nearly killed Jman, thats why Jman shows Tsunade, Kakashi and Yamato the big scar on his chest and says he has only been close to dying twice. Pretty much the Frog holds the key to reinforce the seal or to open it, but the scroll also holds a design for a Jutsu that the 4th left behind for Naruto to learn. The frog says that when he is talking with Jman (Jiraiya)
Damn, you're a faster typer! hahaha. You're ideas are alittle far-fetched compared to mind though... I'd re-think everything if I were you! haha