How to Resume quiz - get credit for questions already answered

You can turn on Self-paced Learning in the TOC settings to have learners forwarded to the same slide they exited from when last viewing a module, which is part of what you wanted.  But this doesn't store their quiz question scores, just their new starting point slide.  Personally, I find this behaviour tends to annoy and confuse learners more than help them.

Your LMS may be able to use Resume Data to bookmark progress in the Quiz, and start again from a certain point in the quiz. But I think you'll find that it still may mean the questions that get skipped don't get scored properly.  You'll need to ensure Never Send Resume Data is set to OFF in the Captivate LMS compatibility settings to test this with your particular LMS. Some seem to know what to do with Resume Data but others don't.  I don't know the exact functionality of your particular LMS, so you'll need to do some testing with Resume Data turned on to see if it works or not.

I can understand wanting this kind of functionality for quizzes that have dozens or hundreds of questions, but quite frankly, it only takes seconds to answer typical Captivate quiz questions.  So going to all this trouble because someone might want to quit a quiz after three questions seems like a lot of trouble for very little advantage to me.