The decision has been made. I'm foregoing any more attempts to save data off my old drive and have actually started rewriting my ENTIRE manuscript, not just the lost half. I knew I'd have to do some fairly heavy editing of what I already had anyway, so I figured I might as well just start it all now rather than wait until I'd finished the whole thing and have to go back.
So far it's not nearly as painful as I thought it would be. In fact, I was inspired to add a prologue that set a whole new tone for the book and introduced a character I hadn't met yet, so that was kind of interesting. I'm also currently reading "Writing the Breakout Novel," and I'm already thinking of ways I'd like to tweak this story based on the suggestions in the book (which, by the way, is awesome), so I'm starting to think this whole experience can be chalked up to God knowing it would take basically destroying my old WIP for me to go back and make the changes I really needed to make.