1) Yes models can be multi-textured.
2) Assume yes until proven otherwise (if you mean models are just 1 single group). I haven't seen a sins mesh yet, but i do know that sins can support both solid, and non-solid mesh's.
3) Guessing the average poly counts to be around the 1k-2k area for frigs, and around 4k+ for cap ships, and structures. Dont know the max polys the engine can handle yet. Obviously less polys = better performance.
4) We don't really know yet. From the looks of things they went large.
5) From what i hear yes (not confirmed yet), but it will cause tremendous performance hits, and lag. so it is not advisable.
6) See number 5
7) you obviously just did

8) The Forge Tools will import models into the game, but not export models from sins. Importing from 3ds is not supported. A third party Milkshape 3d plugin is in work for sins model exporting/importing. Also a 3rd party ship editor.
9) You can use modeling programs like 3dsmax, or lightwave to create models. However the Forge Tools wont import from those formats. I can't say which tool they used. I'll let a dev' contact you about this.
10) The models have self illumination, specular highlights, reflection, bloom, team coloring, and normal maps (all done through texturing) They also have blinking navigational lights, and other effects. If you are talking about self illumination effects like on some Star Trek ships. Some sins ships already have effects like that, but not as noticeable (take a nice close look at the Akkan battlecruiser). As far as i know rendered shadows are not supported. Which is fine, because it only drags down performance.