How to merge coplanar surfaces?

 From:  chippwalters
7058.3 
I don't think that will work. Consider this model:
https://altuit.cloud/web/dbpub/3D/SolidProblem.3dm

Here's a picture of the issues:



1. How to get rid of the dividing line and merge the two rows into one?
2. How to get rid of this rectangle which is part of the solid?
3. Why is the render of this area funny? Is it an OpenGL error?