It would clearly be cleaner if you fully moved everything to Canada (and I wouldn't be too confident that the Canadian dollar is as low as it can go) but I think you'll be okay if you do it your way. I actually think your greyest legal areas will be in Canada, rather than the US.
You don't necessarily lose your state of residence when you move out of the US for a period. For example, you retain the right to vote when you leave but voting requires state registration so you'll remain a resident of the state you left for that purpose. Some expats, in fact, have the opposite problem, that they no longer want to be considered a resident of the state they left so they don't have to file resident state tax returns but the state will use their voter registration, drivers license, address in the state and whatever else they have there to argue that they continue to be residents even while not present (California, New Mexico, South Carolina and Virginia are famously bad for this). While the laws about residence vary by state, for a drivers license you will generally be perfectly fine if you just assert that you remain a resident of the state in your absence, if you'll receive mail they send to the in-state address you give them and, to be completely anal about it, if you retain whatever they would ask for if you applied for a new license there (if they want a bill or statement with the address, maybe leaving a bank account or credit card there might do it). In fact, you might want to contact the DMV to see if they have a way to register the fact you'll be away for a while so they'll know you will be voting absentee and that you won't be available for jury duty.
For the car the issue is even more straight forward, since you don't even have to be a resident of a state to have a car registered there and the registration in the state is more of a benefit for the state than it is for you. You may have to take the car back to the state if it needs an inspection when you renew the registration, and you'll need to make very sure your insurance will cover you if you spend extended periods away. Beyond this, no one there has much reason to object if the car isn't present in the state all that often.
It is in Canada where the issues get fuzzier. The second link you cite does indeed allow you to temporarily import the car for 3 years without registering it in Canada, but that is federal law while driver's licence and vehicle registration requirements are governed by provincial law. The exact laws may vary by province; I'll stick to Ontario since it is the only province I'm familiar with.
Ontario law says you must get an Ontario driver's licence within 60 days of taking up Ontario residence but you cannot do this since, while they would take your US license in exchange for the Ontario one, you would no longer have the US license and there are restrictions on what an Ontario-licensed driver can do with a US-registered vehicle in Ontario; you would mostly be restricted to using it to do the things you would need to get done to re-register it in Ontario. Your position, then, needs to be that you are just temporarily resident (i.e. visiting) in the province while you are there, so as a visitor you can continue to drive your US car with your US license. The fact that the border officer allowed you to temporarily import the vehicle for your stay without RIV registration (it would be good if they gave you a paper indicating this, though I'm not sure they will), requiring you to keep the US license to continue driving the car, should be offered as evidence that your stay is temporary and your continued use of the US license is proper.
The difficulty with this position is the cognitive dissonance caused by the fact that you almost certainly will be calling yourself a resident of the province for other purposes, in particular for income tax and for provincial health insurance (I'm positive you'll need the latter; even if your employer offers health benefits they will only cover what the provincial health insurance doesn't cover). A Canadian resident moving between provinces would normally change their driver's licence and vehicle registration at about the same time that they changed their health insurance. Fortunately the exact definition of "resident" tends to vary from benefit to benefit (or obligation to obligation), so I don't believe they can necessarily use the former as evidence that you should be considered a resident for driver's licence purposes as well. In practice you should be okay.
The key take-away from the link above, however, is that you should get an IDP to go along with your US license, since one is required if you are going to be driving as a visitor, in Ontario at least, for more than 3 months. This requirement is nonsensical, in that being in the country for more than 3 months doesn't increase their need for a translation of your license that no one will need to look at in any case, but I think is their way of "encouraging" you to get a local license instead. If you aren't going to be getting the local licence you'll need to be scrupulous about keeping the IDP current (I think they generally only have 1 year of validity) to avoid any risk of being "encouraged" with a charge of driving without a licence. If you do this they shouldn't be able to find much to complain about.
