Good day,
I am an expert in elearning systems and development with over 15 years of experience. My total development/design experience exceeds 20 years or which over 10 years on WordPress & other CMS's.
Rainmaker is a platform to host WordPress and could provide some additions, but mainly it is aimed at sales and marketing, so it is not a must and you could manage without it.
On the other hand, you have mentioned WPLMS which I like so much as it is full featured theme and LearnDash as a plugin, please be reminded that WPLMS & LearnDash are both LMS's; WPLMS could have more features but it mainly lacks to SCORM player which plays a vital role in any LMS; each one has good features, but probably it is better to decide using one rather than both.
All other LMS features are almost the same, but in a different way.
Using LearDash, as a plugin, required a theme, any responsive theme could be used.
I am interested in your project, upon initializing a discussion at your side, we could discuss this further and I could send you links to my work.
All your mentioned features are OK, yes, I can do them all.
Best regards,
SolutionsSP