1. I use nothing but premium. Kinda depends on how often you want to clean your injectors.
2. Same drive train. Same chasis. Same body. Different trim. If you like how the base sits you, then go for it.
3. Don't know.
4. A lot of guys do better than the sticker. Haven't seen too many get less than 20.
5. 50 bucks. 4.43 per.
6. Keep looking. I would think that you find a Limited under 50K for around $12K.

Mods are few and tend to be pricey. You better like it how it comes out of the box. Love mine and have for over 4 years.