Importing from VGP should be okay (I used Amazon, but they don't sell the 3DS anymore). If you set your 3DS region to Canada you can use your credit card on the eShop.
Yes. Just make sure you set your region to USA and you're good to go. Just remember to set a zip code that doesn't have sales tax - otherwise you would need a bit more than $50.
My wallet is facing an inevitable destiny ~