Twilight and Thea were developed from Kerkythea (which is free, but takes longer to learn) Materials from Kerkythea can be used in Twilight, so you can develop your own materials in Kerkythea and use them in Twilight. Twilight is well worth the money but if you are really strapped for cash try Kerkythea first.
Twilight uses the render engine from Kerkythea, but Thea render has different core and material system (even the developer is same as with Kerkythea). Thea can import Kerkythea scenes, but it does a one way conversion.
In SU, a polyline does not exist. So it is now a series of connected edges. It might be considered a "curve" if it is welded.
Are you getting any actual errors? Or how do you know its not selecting it? You might open the ruby console and try it again and see if any errors are posted to the console. Thanks!
That is big and long. Ken is right. Get rid of stuff you don't need and split the file into manageable chunks. Text won't show in SketchUp anyway so it can go.