Hi Uwe, i've been using SCORM at work for weeks, i think i can help a little.
Point by point:
* SCORM 1.2 Multi-SCO - Package
* 4 SCOs
Perfect, you can include in your package any SCO number as you wish, the only rule of thumb is that in a SCO you shouldn't add a link to the contents of another SCO. It's important to remember that all navigation in SCORM 1.2 must be handled by the LMS.
* course-navigation should not be visible
You have to configure this in Moodle. SCORM 1.2 specification doesn't include navigation (SCORM 2004 does), so there isn't any way to configure this from inside the package.
* i want to load/initialise a certain SCO with javascript
Check this link (http://www.adlnet.gov/wp-content/uploads/2011/11/apiwrappers.zip). I'm sure these javascript files can help you. You can also read the javascript files in the golf example to get a grasp of how to initialize/finalize a SCO.
Check also here (http://www.adlnet.gov/wp-content/uploads/2011/07/SCORM_1_2_pdf.zip) for doc named 'Runtime environment', for knowing about all the functions the SCORM API has.
I want to link from one SCO to another scorm.com - Multi-SCORM Example
There shouldn't be a problem if you make sure it opens in a new window. Remember, you musn't link another SCO (or external site, SCORM packages are self-contained) within a SCO.
This site helped me also, if you need more info (http://www.scormcourse.com/scorm12_course/home.html)
Hope it helps a little.