If they've changed your job, TN-1 is not an option plus you cannot be self-employed on TN-1. You can be sponsored for TN-1 by company A while working for company B, i.e. sub-contracted, but it must be arm's length, i.e. you must not have a controlling interest in company A.
If they're unwilling to sponsor you for a visa and you want to be an independent contractor anyway, the only real option is E-2, i.e. treaty investor. However it's tricky to do if you're the only person employed by the company you're setting up because you're supposed to "control" it, not be employed by it (but on the other hand I know people who've gotten E-2 and their only employee was their wife, pretty much).
E visas are by far the most complex non-immigrant category to apply for, requires proof of funds, proof of investment, business plan, etc. Investor categories are where finding a really good immigration consultant can help a lot because they have "fill in the blanks" applications.
There is more information here:
http://toronto.usconsulate.gov/content/ ... ment=evisaE is unusual as far as Canadians go because it requires an actual visa, you cannot apply for it at a POE.
Steve.