Hi, my name is Matt S Rinc and I can help you - a software developer and webmaster for 22 years and involved in multimedia e-learning for adults in last 5 years.
I understand your requirements, have Storyline 2 and have done e-learning projects with it - they are private (local high schools) and OHC (cannot reference). Still importing your powerpoints, creating quizzes and accumulating results at the end will be done well.
Please provide your questions, answers for each of them and which one is the correct. And also can the learner repeat answering on the same question (enhancing final result) or the "story" continues with the next question (and there should be the option to take a quiz again).
Please also state what to do with the results. Articulate has its own (paid) portal for classes or a special PHP script can be called (for submitting results). They have a software to check those results that get saved to a website. This all stands if you want more analysis - you can also just have results submitted via e-mail or nothing at all.
I will respect your branding, colors, fonts yet might introduce some good practices of layout in e-learning modules (e.g. similarity of colors, empty space etc so called "gestalt" principles).
Looking forward to your reply. The final project can be huge yet manageable to upload to the cloud space (Google Drive, Dropbox) since Freelancer's project limitation for file size is 500 MB.
Best Regards,
Matt