First, 400 pounds is a pretty beefy fridge, most basic units are a lot lighter. 400 pounds is coincidentally the top end of the average weight search AI gave me too, the lower end being 200 pounds. I've moved a few fridges over the decades, they'd have been hard pressed to get a 400 pounder wedged in there like that.
Second, a fridge is mostly empty space. The weight is certainly not distributed throughout. If they put the heavy end (usually where the compressor is) hanging out the back, they probably wouldn't have made it very far anyway before the thing ejected itself. They are primarily difficult to move because they are bulky and lack safe handholds for lifting.
Third, police modifications adding weight would necessarily require modifications improving the suspension. It would be pretty bad design if putting three 200+ adults in the rear of a police wagon were enough to make the vehicle unsafe.
This is all a pretty dumb thing to argue about. After all, I agree that the cop in this case was an idiot. That's mostly because storing a fridge on its side is a dumb move, but also because I do actually believe that storing it as we see in the photo would be bad for the car too. Fridges have lots of sharp edges, plenty of opportunity to destroy the interior, shatter a window, or cause an accident. I just don't think weight or its distribution is the problem.
You want mpd to server and play the music, connected with a web front end (there are a few to choose from) accessible on the private store wifi. You should probably serve this frontend only to a certain machine on the network (like the managers computer in the back) and lock everything else out. The last time I ripped CDs on Linux I used whipper, which I believe was the successor to morituri. This is all only legal if the CDs they have already included the licensing fees to play them publicly or are themselves freely licensed. There are sources of freely licensed music out there that you can play publicly without paying.