Lot of questions there, none of them with simple answers.
I like Blender Internal. Much faster results, full use of all features Blender has to offer.
Once you learn BI you can do anything. Many people disagree with me on this, it is just my opinion.
You need to render out still images and combine them later in a video editor. (which can be blender though I highly recommend using an industry standard NLE)
You will add your audio in post.
Faking GI in blender is easy using AO or spotlight-spheres or both. Lighting to me is much more complex than just “faking GI”.
GI, AO, Raytracing, Indirect Lighting, Photon Mapping all of these can be faked or baked using one method or another, None of these things will make or break your animation.
If you want to use Blender Internal, and you want fast results with decent quality, use the light rig and settings in the file I am attaching here. No raytracing, Buffer Shadows = Quick renders
P.S. and for everyones sake render in 1280 x 720 or 1920 x 1080. I wish we could all just decide to use one ratio and be done with it. Ban 4:3 aspect ratio!!!
lights-camera-action.blend (159 KB)