I posted my dilemma regarding braces on the MakeMusic forums. A kindly soul took a look at my brace and managed to make it himself just using the editor in Finale's Document Options. Somehow in my previous efforts I missed the setting marked "Center Thickness," which was the catalyst for all of my adventures in Illustrator and Photoshop.
While I am now able to achieve my desired braces in Finale, this does not excuse the truly miserable time I had trying to import graphics. Maybe it's just me and the combination of software and hardware I have on my system. Maybe I did or did not check a particular setting when creating my images.
Oh well. At least it works now.