I followed the advice that is presented to me as the end-user, and I changed my settings in FirefoxPortable\Other\Source, where FirefoxPortable.ini is but when I save the file in notepad, then re-launch Firefox the 32-bit version doesn't show up.
My metric for success is if I can get a game using Shockwave player to function, since Shockwave is separate from Flash, and any software that requires it now says there needs to be a plugin, which isn't loading because I'm using 64-bit Firefox.