I can speak to the 3D printer questions, as I've used MoI a lot to design printed parts for my projects.

I also have Simplify3D and use it with my Robo R2 3D printer. I export my parts from MoI as STL files and Simplify3D has always imported and sliced them with no problems.

My projects require good precision as I often press bearings into holes or press 3D printed gears on to motor shafts. Here's a tip: In Simplify3D I scale the part to 100.5% This is to compensate for shrinkage as the plastic cools. Experiment and find a value that works for your system.

Ed Ferguson