TN VISA tricky questions

HI,

I am a Canadian citizen who just got a job offer from an US company. I have the following questions:

When you cross the border and ask for the TN Visa, are you allowed to go back into Canada right away? I am not sure if they will approve my TN so I want to make sure I have it before I make arrangements to move to the US. So ideally I would cross the border, get my TN approved, go back to Canada, and look for apartments in the US and move in around 2 weeks. Is that possible?
I don't want to quit my job in Canada until I make sure that my TN gets approved. Is that possible or once you have your TN approved you are suppossed to quit right away or even before? I would quit the day after I get my TN basically, but would like to give 2 weeks, thats why I am asking.
I have a technical degree in fashion design + over 10 years of experience. Fashion Design is not in the NAFTA list but Industrial Design is. I am thinking about applying as such. Would this be an issue if the job description/job offer calls for Industrial Designer?
Could my common-law partner (we are not married) come with me as a visitor for 3 months and look for jobs from the US, and once he gets a job offer then cross the border and apply for a TN?
I have heard that the agents at the Quebec/US borders are very picky right now with TNs. I heard that the best post is the Toronto Airport to get your TN approved. To go to that post, would I have to actually take a flight? or can I just go to the airport, get the TN approved and then go back to Montreal?

Thank you so much for your help!

Non Immigrant and Immigrant Visas