1) Cops are not required to enforce every law in every situation. Therefore, there is nothing illegal about them not giving a ticket to the driver for the tail-light or the open container. Your offense is still illegal in this regard.
2) If you confessed in front of the police that you were drinking and you are a minor, then they will testify to this effect. If there is no physical evidence that you were drinking (field sobriety test, breathalyzer, swerving while driving on camera), then it is your word against theirs. The court tends to side with the police (understandably), but if you have enough character witnesses and witnesses of the event, then it is conceivable that a jury would find your not guilty.
3) Going to trial is a long and very expensive process which is basically designed to keep poor people from going to trial for minor offenses. Take note that everyone you talk to who is part of the legal system will try to convince you that it isn’t worth it to go to trial…this includes your lawyer, the judge, and the police. Your lawyer agrees with this because s/he gets paid for doing less work if you don’t go to trial. However, a good lawyer can get the court dismissed without it going on your record, so it might be worthwhile to hire one.
4) If you plea bargain the court is likely to grant you some kind of benchmark probation (not actual probation, meaning you don’t have to check in with anybody…but if you break any more laws you will get tried (unfairly) for this offense). If you pass probation, they dismiss the case with no conviction on your record. However, the ticket is still searchable by various agencies. Plea bargain basically means that you accept that what you did was illegal and you are showing remorse by offering to save the state time and money and admitting your fault. In return, they offer you a better deal than if you fought the case at trial and lost. However, this ‘better deal’ is expensive (you pay court fees and monthly fees for probation) and dangerous (if the police get so much as a phone call that you have broken a law, they can retract your probation and try the case…ie if your girlfriend called the police and said you hit her: go to jail, even if you didn’t). If all you have is a ticket (and not a court date), then I’m not sure if plea bargaining is an option. I think you just pay the ticket and it’s over.
5) If you move out of state, I believe it is not possible for a non-governmental agency to trace this ticket/charge. However, I think Texas police will always have that ability, even if it is dismissed. However, if you give an address in Texas on a rental, credit or job application and they run a background check on you- it will possibly come up. It’s possible to get some kind of assurance from the state that it won’t (via a lawyer, usually), but the state does not always do what they say they will do.
6) It’s not the end of the world. Even if you pay the ticket (hence plead guilty) or go to trial and lose (hence are found guilty), it will probably not hurt your chances of doing anything you want to do in life. It can come back to haunt you if there is a future trial that involves alcohol (say a fight in public), and then they will use the MIC as character evidence that you have an “alcohol problem”. But other than that, you will have no trouble getting into a good school or getting a good job just because of an MIC. If you’re really worried about this, get a good (and expensive) lawyer. Expect to spend at least a couple thousand, maybe as much as $8000.
NOTE: I am not a lawyer and don’t really know what I’m talking about. The previous advice is my opinion based on what I have perceived about the legal system on my own and through friends.
NOTE: There are free legal advice forums on the internet where actual lawyers can give you much more accurate advice. I would advise that you post your request (with somewhat better organization) on multiple forums.
Good luck.