@ChristynaMoore
Interesting use case. Canvas isn't really designed for interesting cases. They target the middle 60% of users.
The short answer is no, there is no way to link them automatically to get everything you want.
You can export the grades to Excel, do the calculations for the composite pseudo-assignments there, and upload them back. If you (or someone you know) has programming skills, you can download the grades, have the program compute the grades, and then submit them back to Canvas.
It can be done without manually entering the grades, but there is no built-in way in Canvas to tie assignments together like you're wanting.