It is best you consult ia lawyer n private to review your specific situation.

In general, 60 day grace period which starts after the last day you were on TN employer's official payroll.

I recommend consultation with an experienced immigration lawyer.

The EAD issued by USCIS is for other purposes, such as getting SSN. among others. This is not authrization for employment, per se. Consult with...

Consult with a lawyer to address the problem from your perspective.

Yes. You may transfer to the new employer when USCIS receives the petition..

Best to consult your local attorneys about business formation rules and regulations.

The US embassy in your home country will asdvice accordingly.

Duplicate question - previously asked and answered.

The approval of I-140 and I-485 and subsequesnt loss of job does not invalidate EAD issued on approved I-485.