CSD18542KTT: Power Dissipation and Thermal

Part Number: CSD18542KTT

Hello, I have a basic question concerning junction temperature on my fet and also concerning duty cycle.

I plan to use CSD18542 on the power block for a 3Phase motor.  The motor draws current in the order of 1.4A for about 50ms.  The Period I (hopefully correctly) calculated from the image shown below at ~ 80ms.  Which makes the duty cycle 0.62.

The image was obtained by using a clamp current probe on phase A.  Can you let me know if this is how u would have calculated the duty cycle.... that is the time any one of the 6 fets are conducting?

also, can I calculate Tj like this:  Tj = Tc + Id x Vds x D.  Where D is the duty cycle.