1) Physical awards don't generally interest me. I'm always more interested in early access or in game perks but I would be hard pressed to say no to a plushie of Screech. Also a keychain of the protagonist's butterfly brooch might be cool?
2) From most to least interested: Thrace, Kadan, Roxas. Iandir, Aiden.
3) 5 years is definitely a /long/ time, and I'll echo others about being leery of funding a project with that time frame. I've been burned in the past with promises of less development time. I can appreciate you guys being upfront about a long wait, though! I'm going to infer through your post that each route might take us to vastly different places (or at least different locations within the same area), and if that's the case, my usual suggestion of trying to reuse a bg a few times becomes harder to pull off. Perhaps a good compromise would be to get the /most/ important bgs for a route done. Reuse what you can in a route and then update with less important ones as they are finished? You could also go with a placeholder image for similar locations. I know in a lot of games, general outside scenery or travelling BGs are reused a lot. I personally very rarely notice this, as I'm far too focused on the characters or what's happening. You could also perhaps add a stretch goal with an appropriate amount that would allow you to hire another or multiple artists to help?