Agreed. Presumably you have an original receipt or email from ACV confirming what you've booked. And hopefully some pictures or other proof of what you received. that's a bait and switch move. And since you've already gone through a lot of stress (like going to the front desk to get things sorted out each morning is a pain, calling up ACV during your vacation and after your vacation is a pain, the vacation itself was a pain), might as well go all the way. I recently had a bad experience with a VRBO rental getting my deposit back from the property owner. Took me 8 months for 500 euro (had to track down the owner where he worked and start calling him there). For $3800 I'd be even more enraged. It's not just the money...it's the principle. And...after all this stress (and hopefully ACV makes you whole) you'll have deserved a real vacation.

As far as the flights go, you're probably out of luck (misinformed agent).