Hi. I saw what you wrote, and I'd just like to say, that you aren't (weren't) alone in this. In, pretty much all of it.
1. 'It' is something that really only school-leavers can see. When I was in school I had pretty much the exact same viewpoint, buut, now that I'm out, I know exactly what 'it' is. 'It' is the realisation that you just didn't do enough, that you could have tried so much harder, and gotten a great grade, that you could have been proud talking to all of your mates once you left school, when they (and they will) ask you 'What GPA did you get?". 'It' is both the biggest hunk of bullshit, and a very painful revelation. Believe me, you may be able to get into the course you want. May. But, after that, what about a job? Believe me, if the people in the job and the people in the uni have to make a choice between a 4.0 and a 2.2, it's quite obvious what you want to get, and, although you may be 'above the bar' for your specific course, doesn't mean that you're actually going to get in. However - I can understand that if I were to be still in school now, I'd still be slacking off, because, pretty much, 13 years of school just Fuck Your Mind Over. Maybe your guidance counsellor and Dad are just too old to realize that.
2. Apathy and a loss of connection with your parents comes at that age. It'll pass, but, for now, hate your parents - Go to parties - spend amazing amounts of time in your room. I mean, you're a teenager, you're basically entitled to this shit. Start giving cheek to adults, get a wierd haircut. Sure, maybe a little old lady won't get into an elevator with you, but it'll be fucking hilarious when you challenge everyone's preconceptions. Also, 'lazy' is another thing you're allowed to have when you're a teen. As long as you kick into gear when it's time to move out, it really doesn't matter.
3. 'Gifted' is something you shouldn't really take for granted. If you can pick stuff up quickly, if you are fairly good at subjects now, really good if it's interesting, and amazingly good when you truly knuckle down on it, then you'll know what I mean. Sure, gifted is boring, but I bet you'd rather be gifted than not, so quit wasting it.
With all that said, I'm not the best role-model. But, I was in your situation about 11 months ago, so I can empathise.