Jack, sorry mate, but that silver unicorn blood is not good news.

Pass a good magnet through the fluid, and I bet a lot of metal will stick to the magnet.

Something in there is foobarred.

I would be getting back in touch with that shop real quick.
At least they did follow up and advise you, so they might have some integrity and pay up to put it right.

As far as checking your ratio goes, your dad's suggestion is the easiest way.
Accurately mark a reference point on the tailshaft and the diff housing.
Also one on the wheel and guard.
Turn the wheel exactly 1 turn, count the number of turns the tailshaft makes, and the incomplete turn is the .88 (hopefully) you are looking for.

Hope you get out of this OK.

PK