A Visa is required and it may take around 3 months to get a visa since US will do a background and you may have to fill some extra form since your greencard is expired.
Sales doc is required and in regards of passing etest with 240,000 miles it will but you make have to spent some money and it all depands what kind of condition the car is now.
First you have to make sure that you will get us visa to go back because lately lot of us visa are denied for some reasons. Investment in us is great idea and you will never go wrong with it. Before buying make sure u have us visa.
Be on safe side add your suv on goods to follow list. I moved from us almost 3 years ago i just got my suv lucky i added on my list or you have to pay all canadian tax and its not cheap.
Only for the primary appliant but they may ask or may not ask at all about rest of the family. Dont worry you are coming to canada legally and you have the visa and what ever happened in usa leave it all behind and move on with your life.
Yes they will ask your status in USA. Good advise is that you just have to be honest and tell the truth. If you lie and they find out than you will be in more problem. I moved from USA almost 3 years ago like you with all my stuff and they was no problem at all. Good luck