Well, the position-thing is caused by you changing from World- to Object coordinates during modelling, or mix model parts made with different coordinte system.
When you mix that, stuff starts jumping out of its propotions when exported. Stay to eighter one, world- or object coordinates. I only use world coordinates- always and everywhere. Then I know that my models stays clean. Object coordinates confuses me. But then again, I have Altheimers Light :)

Can't rate your products as this only can be done by TS staff, trusted raters and buyers of your models. Models look nice, but you should work on the rendering part. The way you present things here DOES matter. Turn on some area lights/area shadows. Make your previews look nicer. If you have the Advanced Render Module that shoul be an easy task. Good luck, mate.