I don't think anyone's going to think less of you because you enjoy wet and messy diapers. Most of us in this corner of Zity also do. That's why were here. And when I was your age, I only wish I had the advantage of forums like this one to answer my fears and questions. As a young person, I once had the same problem as you: fear of discovery. And I eventually solved it (read my profile and blog) by doing exactly what others here are suggesting: I moved out and got my own place. It wasn't much (1-1/2 rooms), but it was my very own, and I could mess in my diaper to my heart's content. I wish I had done it earlier.
To answer your other questions,
1. The best way to hide it is to scrape off any excess poo, then wrap it up in a plastic bag (two if necessary), and take it to the nearest dumpster (preferably at night).
2. You really can't mask the smell, although you might try taking chlorophyll tablets which are supposed to kill some of the odor. Eating certain foods (and staying away from others) also affects odor, but you'll need to do some research on which ones. You can also poop your diaper in the bathroom (turn on the exhaust fan to mask noise and remove some of the odor), where such smells are to be expected.
3. What to do after you poop is whatever makes you feel the best. Sometimes I like to sit in it.
4. You should wear the messy diaper for as long as it makes you feel good (although living at home, you may not want to leave it on for too long - other people are going to want to use the bathroom.
5. Here again, there is no "best" position. It's whatever makes you feel most comfortable. Personally I only like to do it lying down on my bed (possibly because it makes me feel like a small child again). And once I've filled my diaper, I can just lay there enjoying its messy warmth. Sometimes I even fall asleep.
6. Unless your poop is very watery it probably won't leak (if you feel diarrhea coming, then get on the toilet, and forget about the diaper. If it's urine you're worried about, you may want to release some of it in the toilet before you pee in the diaper. In either instance a good plastic diaper cover is recommended, both to guard against leaks and to help mask the odor.
Even though I'm certainly no expert on this subject, I have been doing it for many years, so let me know if there's anything else I can answer for you. Best of luck!