I've gone through all your steps for setting up Analytics, and I'm currently testing it, but it's only partially working. I've gone through the steps again to double-check, and I don't think I missed anything, but since I can't quite wrap my head around how it works, I'm hoping I can explain my situation and you might have some ideas about where to look for a mistake!
When I test this myself, I can follow my steps in real-time all the way through to the receipt, but no goal completions are being logged. When I look at the funnel visualization, I see data in the cart step, but zeroes for the checkout and receipt steps. The real-time data shows me on the mydomain.com/cart page (which is the sidecart overlay), then on mydomain.foxycart.com/checkout, then on mydomain.foxycart.com/receipt. Is there something I've missed about setting up analytics so it knows it's looking for the foxycart domain /receipt page and not mydomain.com/receipt?
I can whisper more details if that would help. Thanks!