I don't know if this will work for what you need to do with the data afterwards, but have you seen this widget? http://captivatedev.com/2012/11/12/adobe-captivate-6-x-widget-google-l ms-with-email-reporting-2/
It would allow you to write user variables and quiz data to a google spreadsheet, which would take care of number 1 (and I think number 2?) depending on your setup. I don't know whether or not a google spreadsheet is something you can use, but it's an alternative to an LMS.
For number 3... what if you executed that JavaScript for both success and failure of the last quiz question? No idea how that would affect the reporting, but you could try it. Alternatively, you might be able to do without the quiz results screen-- just have a single slide after your last question, and execute the JavaScript upon entering that slide.