Please help! what is the best way to build stronger, more defined abs?

Try cable pulldowns: You're going to need to diet and be hungry for a fair part of each day, and not "reward yourself with food." you'll need to do some serious aerobic exercise. As you lose most of your body fat, start developing your abdominal muscles. Especially, don't neglect exercises like cable pull-downs for heavy resistance. Exercise for your health as well as for good looks.