@ReneeQuick In Canvas, the assignment group subtotals (and the course total when assignment group weighting is off) are always calculated by dividing total points earned by total points possible. The only way to weight assignments equally is for them to be in assignment groups where all assignments have the same number of points possible; then assignment group weights can be used.
In your LTI, you may be able to switch how grades are synced to Canvas. Instead of "assignment raw score," you can choose "assignment weighted score" to normalize the points possible. (When I try to link to their documentation, my reply gets flagged for moderation.) I hope this works. It would be the most elegant solution.