Sarah, I'm glad you were able to get this working. it sounds like you created a dedicated user in the scratch org different from the default scratch org user? If so, there may be a simpler way to do what you're wanting. Please see the user guide topics for
Creating Projects:
That covers various permutations of Salesforce org types, file storage formats (metadata format vs. source format), etc., and how you can create an IC2 project for each.
I hope that helps as well.
Regards,
Scott Wells