You might be overthinking it a bit, but that’s the fun part. With your diet plan looking good, I’d lean toward more weighted ab work and less HIIT (which can sneak up on you fast in a bad way if not careful. Info HERE).
Now, “more weighted ab work” doesn’t mean more exercises. Just find a couple you really feel (almost like a cramp) and keep them focused and concentrated.
I like Coach Thibaudeau’s philosophy on ab training: fail as fast as possible. Meaning, make it so you can’t get over 8-10 reps, even with a basic unweighted crunch. That involves bracing like you’re about to get punched in the gut, hard top-end contractions, and milking every rep.
Here’s the most I ever learned about ab training in 30 seconds: