I got a measuring tape w/ a hook, yanked the two ends together round my waist criss cross style tightly to get the closest approximation. Is that cheating? Why or why not?

A measurement is supposed to be consistent. So, if you do it the same every time, you will see progress in the same every time.

For true measurment though - as "what would a seamstress/tailor do" they would measure so that the tape touches your skin all around at your narrowest point (making it your true waist), but they wouldn't pull it tight.

You are doing it good.. Don't overthink so much!

I normally measure my waist just above your pelvic bone.