I think you are on the right track. A couple of things to be aware of. Your film is likely fogged after sitting around for so long. I second the recommendation to use an anti-fogging agent (benzotriazole) when you are doing your testing. Second, because the effect of fog is to increase the base density of your negatives (and therefore grain), I would stay away from Rodinal, even as a stand developer. There is nothing wrong with Rodinal inherently and I have run some tests with it using the stand method -- it is great for certain applications, just not this one. You want a developer that is going to decrease the appearance of grain -- something with a solvent in it like D-76 or ID-11 1:1. Your idea of developing a strip of film is right-on. I would clip off about 10 cm of the film and give it "best-guess" development. Start with rlouzin's recommendation of a 50% increase in development time, but with a good anti-fog agent in the mix. If you get interesting results, post 'em!
Edit: I wouldn't be too worried about rust inside the film canister. I don't think you would get the same condensation inside as outside. On the other hand, if the whole works were submerged in water, the film emulsion will be a fused mess inside the canister (don't ask me how I know this) and it is unlikely that you would be able to unwind the film without ripping it, or salvage any images.
