Hmm.Well the solidworks file I uploaded is a 2016 version. I'm not sure why the parasolid wouldn't be importing well though. Are the parts broken or just things like the screws? Have you used the auto-fix features in the import diagnostics? Those usually work well. The overlapping solids are most likely the screws, which overlap on purpose. I definitely wouldn't use the feature editing, that never works. I would just build on top of the existing solids by adding features, or potentially using things like move face, etc.