Don't worry so much about other people's feelings. If you have to make a change in your life that affects others, then by all means give them fair warning and try to help them prepare for the change. But they are adults too, their feelings are *theirs* (not yours), and it's up to them to deal with their feelings. If an upcoming change is reasonable in terms of timing and context, then you don't owe anyone anything more than fair warning. It's your life, and you have to have a free hand in choosing how to live it.
Your parents have had plenty of warning that you would be going away to college. It's natural for them to feel a little abandoned when you take off, but that's their affair, not yours. Promise them you'll phone home on Sunday nights, and depart with a light heart.
Lying to the boss about how long you'll be in your job is generally considered fair game if you have good reason to believe that you wouldn't get the job otherwise. I don't like to tell that kind of lie myself, but most people tend to think it's an acceptable white lie under the circumstances. In any case, that's old history. What you owe the boss now is fair warning so that he has time to find a replacement for you. So tell him that your plans have unavoidably changed and you need to leave earlier than expected. Try to give him two weeks warning before you have to leave. Tell him that you'll ease the transition as much as possible for him, and that you'll be happy to train your replacement if one can be found in time. And then when it's time to depart, leave with a light heart. At that point, you've been fairer to him than most departing employees. He'll survive, he's used to employee turnover, it's just business as usual for him.
You didn't mention dating, but that may be an area where you might have trouble as well. (Or maybe you just have difficulty with disappointing authority figures, and you're fine with disappointing peers.) In any case, it's a good area for exploring the dynamics of how much one adult owes another in terms of emotional commitment.
Dating is *not* about making a big commitment up front and then being obligated to stay with the other person to avoid hurting them. That sort of big commitment would be *marriage*. Dating is what happens before marriage. Dating is about casting a wide net, and testing your compatibility with a number of different partners *before* you make a big commitment.
In dating, you keep the commitment low and only increase it slowly as the relationship seems to be working well. If the relationship starts running into problems, you cool the commitment down. If the relationship fails, you depart with a light heart. You're not bound by the expectations and emotions of others. Presumably they are adults like you and are at least vaguely aware of how dating works. Your only obligation is to be honest and fair with the other person (or as fair and honest as one can be--there are inevitably a few little white lies involved in dating, especially in a break-up). But don't be afraid to move on, even if it means the other person is hurt. The whole idea of dating is to have the right to jump in, test the waters, and jump back out if the temperature is wrong for you. Save the giant, life-long emotional commitment for after the wedding vows.
And turnabout is fair play. If you're in love with a woman and she decides the relationship isn't for her, don't expect to be able to bind her or obligate her with your emotions or your pain. If she has been basically honest and fair with you, then she's a free agent. She owes you nothing more than that. That's how dating works, and it you want to play that game then you have to be willing to be adult about it.
But in any case, don't worry about all the guilt that you're currently feeling. You're expecting some emotional displays by your parents and boss when you leave, and it's making you anxious. But you'll get over it. (Your parents and boss may not be as broken up as you anticipate, anyway.) You're an adult now, and if you want to progress in the world, you'll have to expect to make some waves along the way. Go ahead and hide behind the rules a little bit: If you've been basically fair and honest, then you're free and clear. But in any case, don't feel bound by the emotional upsets of other people. There are a lot of emotionally needy people out there, and if you get tangled up in their dramas you'll just end up living their lives instead of your own. And that's neither fair nor honest to you.