"To overload" means to gradually make each exercise harder each workout. In weightlifting, this means adding more reps, or weight each session. You can try to beat your running times/cardio times but for obvious reasons you eventually wont be able to beat your own times and you will stop overload naturally, because you can easily add a few lbs to an exercise but if everyone could beat their running times, everyone would eventually be an olympic runner. The cardio will help burn extra calories, although I'd limit HIIT to about 2 or 3 times a week, and same with running. Depending on the ab workout, you can do that 3 times a week. Your ab workout should include a rotation exercise, a lateral exercise, a transverse abdominus exercise and an upper/lower exercise (or both upper and lower).
Without seeing your ab workout, I can only suggest that you do the above core exercises, and start out doing anti-exercises with static movement, then move onto dynamic movement, before hopping into core work. This is just a personal preference and it'll help your athleticism too