IMO that's a pretty nice looking car! Monetary value is always in the eyes of the buyer and seller. But FWIW, I really don't think you did too bad at all, and pretty much got your money's worth. Don't beat yourself up over it. Any car if this type, in this price range, will NOT be a truly original 400 that looks that pretty, and WILL have some substantial issues to address. That's just the way it is...
Assuming you were seeking a driver, and not a concourse restoration candidate, I think you did fine, even if it didn't turn out to be what you had hoped. Just enjoy driving it!
