Anyone have any good ideas on how I can rescue this design?
Nah, not really, and why do you care?
Look dude, when you're running chop-shop design (like most of us are, admit it or not) you will encounter a segment of the population that just cannot be reached. There is no amount of design and production you can show them that they will appreciate. Don't even try. It'll leave you old and bitter. Based on everything you've told us about this clown, he's too stupid to realize that he's stupid. I mean for God's sake he made you(r boss) reprint a sign to
preserve his own misspelling. Why,
why are you trying to do this guy any favors?
Take the artwork he gave you and prep it. Show the resultant trainwreck to your boss, and if paycheck says it's a go, let a rip and walk the hell away. This is not an issue of professional pride, here. This is some skinflint bottom-feeder who ought to get exactly what he's paid for and not a single dime more. If he walks out of your shop and looks like an idiot, great! Take pictures. Post 'em here. I'd love to see them.
You've done your job. Don't waste pearls on swine.