It's adorable that you remember the exact date you first saw your abs. Unfortunately, you being just 12 or 13 years old at the time is a pretty significant factor.
Do you think that just maybe you've been working out wrong, or at least following a bad plan all this time?
How do you know your bodyfat is 8.8%? And who told you that was a "near danger level"?
"I know the cancerous tumors on my brain, spine, and lungs are an issue, but my main concern is this annoying runny nose."
How much sense does that make, really?
If you're as skinny as you say you are and don't already have a ridiculous set of abs, it's because, despite your almost-three and a half years of ab training, you don't have any real muscle there... or anywhere. Low bodyfat isn't all it takes to show off abs. It's low bodyfat plus having enough muscle so you have something to actually show off.
This is a large part of the problem. A beginner shouldn't really be trying a variety of workouts, a young beginner even moreso. Stick with one well-designed routine to build a solid base of muscle and strength, and then expand from there. Do this starting today:
Mon., Wed., and Fri.
Squat 2x15 (No weight, keep both feet flat on the floor.)
Push-up 2x15 (On your toes, go until the chest almost touches the floor.)
Lunge 2x15 (Alternate legs, 1 rep left/1 rep right.)
Neutral-grip pull-up 2x15 (assisted if necessary. Could be substituted with inverted rows.)
Plank 2x15-count (Hold the top part of a push-up, on the toes, arms straight, keep the whole body straight. Count to 15.)
Burpee/squat thrust 2x15
Once every set of every exercise is pretty easy (not reaching muscular failure at the end of any set), move to a well-designed program that focuses mostly on a lot of free weight (barbell and dumbbell) exercises.
Do you actually want advice or do you want to keep telling us why you think the problem isn't too much fat and too little muscle? Dude, open your mind and come at this with a new outlook.
Train smarter, like I suggested, and eat better. When I say better, I mean at least three good meals [i]everyday[/i] that make you feel full afterwards. Focus on eating "good food" more often than crap, but some junk food (candy, soda, whatever) once in a while is absolutely fine. The more you can cook for yourself, the better, even if it's just scrambled or hard-boiled eggs. Meat or eggs should be a big part of every single meal. Do not try to cut carbs or avoid fats.
These articles have some good info, but keep things simple overall: