Hi Larry,
I can help with a few of your questions:
1. SigmaStudio includes a hierarchy board feature that allow you to save and recall sub-circuits -- see the tutorial at https://ez.analog.com/message/52938#52938 , and an example using them extensively at
https://ez.analog.com/message/135978#135978
3. Absolutely -- after you compile your SigmaStudio project, use the Export System Files option to create files that contain the needed info. The parameter addresses change each time you add to your project, but the export C header files attempt to automate the process for you. There's an example at How do I create the microcontroller code to interface to my SigmaDSP? Here, unfortunately, is one area where the documentation has not kept up with the Sigma 300 (-145x) DSPs.
7. SigmaDSP IIR filters are Direct Form 2. Double-precision filters use single-precision parameters. Filters have adjustable gain, which may help economize on gain blocks. The Sigma 300 compiler optimizes IIR filters extensively, so cascaded sections use fewer instructions than separate filter blocks.
Best regards,
Bob