Ab rollouts are cool, and high reps seem to work well for them.
I used to do a circuit with exercises like the rest of them you have there, and it never did anything for me.
I like glute-ham sit-ups, also known as Roman Chair sit-ups, for three sets of 10, with a bumper plate held behind my head. The Range of Motion on these is great - legs are locked under the apparatus and full extended, the hip angle opens to over 225 degrees. Incredbily difficult. My best is 10 with 15 kilos. My coach told me that an 85-kilo lifter from my gym who won the National Oly championships could do reps with 45 kilos behind his head.