Multiple Projects with only one quiz for LMS

I think if you're going to be creating SCORM content with Captivate, but need it to work in ways that Captivate doesn't cater for, then you'll need to become more conversant with the SCORM technology yourself.  In short, you're going to need to get your hands dirty modifying some of the files that make up a SCORM package so that you can fool the LMS into working the way YOU want it to.

Here's some basic information about packaging SCORM modules:

http://scorm.com/scorm-explained/technical-scorm/content-packaging/

Note that it says you can specify some objects in a package as being assets, which means they don't communicate with the LMS.  This would seem to be a similar case to what you propose with your scenarios.

This page lays out the XML structure of the imsmanifest.xml file:

http://scorm.com/scorm-explained/technical-scorm/content-packaging/manifest-structure/#

Captivate creates one of these for each single SCO SCORM it produces.  If you use the MULTI-SCO packaging tool, it creates a master imsmanifest.xml that details all of the child SCOs within the package.  You can modify this imsmanifest.xml files using any text editor to change how the package behaves in an LMS.

It will probably take some experimentation and several trial and error runs to find out how you need to configure the manifest so that the LMS only listens to the Case Study and Quiz module in your package, instead of all the other assets that are just there as reference material.