Well, I have tried both, and now I do neither. The money I could have made was not worth the trouble of making it.
If you sell on .ca you will need to have a Canadian return address.
Whether to run ads or not is up to you, and out of my realm of expertise. That said, if your item is already selling on .ca for those elevated prices, there may already be a population of people delighted to get your items for cheaper.
Be sure you know what you are getting into before sinking too much into this. The hassle of international sales and shipping is not negligible.