I can try to take these in order:

1) This is one of those things that just has to be learned, it can't easily be put into words. I mean, some people have theories about anchors and whatnot, but really it's just a matter of training your brain to be in a certain mode, and that's achievable with lots of practice.

2) The vibrations aren't always violent, sometimes they're fairly calm. But if you want to avoid them, you can do that by entering the dream early. The dream will be a little more unstable at first, but you won't feel the vibrations anymore. Of course, entering the dream is another matter.

3) Once the landscapes start to become 3-dimensional, you can stick your arm out and touch them. Assuming your 'real' arm is sufficiently paralyzed, the arm that you are able to move will be your 'dream' arm. Then once you touch something, the dream wraps around you. There's more to it than that, but again it's just something that takes a little practice.

Don't worry if it seems like you don't have any arms. Just send the signal and an arm will appear. What an odd thing to say.

4) Accidental hallucinations -- all the time.

5) I can't help you with this one.

6) I made a new colour once. It was sorta like green, sorta like pink, but not a colour that actually exists.

You know, now that I think about it, this may be one of the rare cases where DILD is actually the better way to go. I'm not sure if your nightmares would appear in a WILD. Also, WILD tends to produce 100% lucidity, which makes for very short dreams (seconds to minutes), for a beginner at least. DILD might give less lucid, but longer, dreams. And DILD dreams might contain more nightmares. But I would still recommend WILD for lucid dreaming in general.