Hi there, I'm Matt Sergei (do call me Matt, please) and wonder - you don't need any of the LearnDash features to score the user, save the results, give them a certificate etc?
Then it might be easier to implement a plugin from scratch.
I understand the requirements yet it appears you have prepared a documentation for them (stated in your project description) - can you share them first?
Otherwise I'm a webmaster and IT developer for 26 years, with developing for WordPress for 11+ years.
Regards, and hope you're safe,
Matt