1. Workout every day and gain size, but, probably not definition, other than fat reduction, just by burning calories. Definition has nothing to do with working out the muscle, for the most part. That's mostly a function of body fat levels.
2. Maybe, maybe not. But, to over-develop your abs seems stupid. Abs, arms, forearms, calves...recover fast. Do em' everyday if you want but, it's not going to help with visible abs as much as just burn calories, and there are other more effective ways to effect caloric burn.
3. Complete and utter bullshit. Some folks have fewer muscle groups, or more groups, in their ab region, but that's all genes. Visceral fat has a lot to do with visibility. Study that here: http://en.wikipedia.org/wiki/Visceral_fat If you look at the picture of me in my light blue shorts in my profile, about 7 weeks from a show, you'll see I have thick, heavily, developed abs from decades of training and heavy lifting. Whoever is telling you this crap needs to be hand slapped a couple of time for being a moron. This year... I backed way off my ab training and my lines were remarkably improved. I let my abs get weaker, and smaller (the picture in the darker almost purple shorts). Somebody tells you that crap, tell them they are the idiot that they are. Anyone with have a head knows better.
Google on "getting abs", read articles here, or go to bodybuilding.com. Then, put your thinking hat on and think this through. At some point, common sense will prevail.
Ab visibility is a function of body fat levels.
Ab development is just that, a function of development, whether or not they are visible is contingent to fat levels. Again, common sense at work.
To much ab development will ruin your lines. Most folks would be idiots to work abs on a daily basis. Unless you need to be able to squat 700 or leg press 1400, you probably don't need your core that well developed, and would do well to pursue a more balanced training regimen.
Developing lean muscle mass, particularly in your legs, burns calories at rest, which keeps you leaner, which makes your abs more visible. Again, common sense 101.
This really gets down to studying the human machine, and then applying common sense to its function and appearance.
Anorexic guys have "abs" but look and are ill. Good overall development is more important.
Whether you do high reps or low reps, again, in inconsequential, for the most part, with regard to visibility. In your case, an overall development program would like be more in order, although you've neglected profile completion, so it's hard to really even to a guessimate.
THINK. Who has the best lines? Gymnasts? Bodybuilders? Look at how they do abs. Think on it. Watch. Likely, you'll find they don't do tons of ab work, but rather they do things for the appearance. Simple things like leg lifts, crunches, and they stay lean. Maybe some twisting core movement for trans vs, obliques, and the like.