I am unable to export my project in iMovie to anything. Even at the lowest resolution.

Try deleting preferences. To delete preferences open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects. Now see if you can export.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

-- Rich