Which CAD files are you using? Are you using student license? Student license does not support changing parameters to a CAD file and importing it in Workbench.
If you have these parameters in SpaceClaim and trying to change it automatically and it is not changing then, I will suggest the following (Because to debug exact reason, one will need to look into code and the model, which I am not allowed to do):
Create a very small test case, do the process that I suggested for a couple of DPs manually while recording the journal. (Workbench>File>Scripting>RecordJounal)
Once you have lines for a couple of design points, you should be able to expand it for all 600 DPs using a for loop, which in turn can be expanded to your original model. As you have already written a script in SpaceClaim this would be a similar exercise.
Finally, there is a drawback of this method, it does not provide you any feedback like the default method until it runs (successfully or unsuccessfully through entire script).
(You can insert some mechanism such as saving project, writing a file showing current progress, etc but I will leave you to explore that)
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