Answers:
1 yes ... just for effectively "painting" your figure only.
2.A variety of reasons including loading into AC3D, also rendering a scene with the figure in it, and if you want to animate it.
3.There is a *polygon reduced* version of M3. Also a variety of figures including M2 and M1 and P2-4. All with lower polygon counts.
If all you are doing is using it as a scale, why not load it once into AC3D, draw a box around it, delete the figure, then save the box as your *measuring stick* in an ac3d format ?
griff