David,
It is obvious you had to do a lot of hard work here. I think there could a version problem between the dsk_app project and the CSL you are using.
In the version of CSL that I have, 3.00.10.02 from 2006, CSL_edma3GetParamHandle should never return zero (NULL) unless there is an error. More relevant to your tests with dsk_app is the fact that CSL_edma3GetParamHandle will always return NULL if the status argument is NULL. And status is NULL in the dsk_app example that I have.
Are you using the same version of CSL that is delivered with the DSK6455, or have you updated it? There should be some library versions mentioned in the README or such for dsk_app. If not, you might want to contact Spectrum Digital to find out which version of CSL they tested the example with.
I am curious what versions and dates you have on your files. And if you would, please paste the CSL_edma3GetParamHandle in this thread so I can compare it to mine.
Regards,
RandyP