Blender will be used, and only blender. No, not that I am a blender nazi but this shit is free. When we use this as a presentation piece or even market it, we'd be shot down if we were asked how we did it and our response was "we pirated shit!"

1 unit in blender space is equal to a quarter of a meter. So 4 units will represent one meter.

There is no hard limit on polygon count; I would estimate 12 000 polygons to be sufficient, though I don't see any problems with going higher. I would ask to be notified in case the polygon count exceeds 50 000, which is a rather high limit.e

No real limit on textures either, but I would exercise common sense. a 1200*1600 bitmap for an arrowhead for example is excessive. For a square of 1 unit by 1 unit I would expect a texture of 400*400.

Finally, everything will be object based. In blender you can export a .x directx object complete with textures, bones, and even animations. Export the object, spit it out to the repository and then we're good to go. So if you're an artist you don't need to actually understand directx.