○ you could claim it,it is usually taxed more in Canada than US, so the foreign tax paid will be foreign tax credit offset the US tax. Or US has the oversea income exclusion, or you could skip it. Either way, It will end up with almost no tax for Canada income to pay US anyway.
○ there is not a simple answer,better to hire a cross-border tax accountant (usually in the border cities in Canada cause very few US tax guys know Canada tax and they charge a lot) at least for the first year and learn the calculations. Many factors to consider. US tax rules change every year and every state is different. It would not be very easy to plan the job/retire in US also.
○ Thank you very much for your kind reply. Any tax accountant recommended? Please PM me. Thanks.