The posters above have done an admirable job in explaining things. Let me add my two cents.
1(a) is less clear about whose Uncle George you are talking about. It could be your Uncle George, or it could be somebody else's Uncle George. It could be a third-person narrator speaking about someone's Uncle George.
1(b) can only be your Uncle George.
This doesn't mean 1a is wrong. They are both correct grammatically.
2(a~d) I think the posters above me explained this as well as it can be explained. The dinosaur became extinct / Dinosaurs became extinct. Just a stylistic difference with no substantive change in meaning. Your 2(a) can indeed be a general statement, identical to 2(b). In fact, I think it can only be a general statement. If you want to make it specific you have to say "This chicken has wings" (presumably to differentiate it from chickens without wings...). And yes, your 2(c) is interchangeable with your 2(d).
3 and 4 > I think the difference in any of these is pretty subjective. They all have virtually the same meaning (except, as lanthas says, 3e indicates your car is expensive, while the other sentences are silent or vague on the question of whether your car is cheap or expensive. Regarding the relative values of "far more", "much more", "a lot more", etc. its all impossible to quantify, so not worth spending too much time on.
My personal opinion is that "lots" has a casual quality to it that is fine for everyday speech, but in writing I think it should be avoided unless your intention is to sound colloquial, or if you are talking about parking lots.
Just to digress for a second, one of my many pet peeves is the misspelling of the words "lots". It is very common to see people misspelling this as "lot's". Makes my inner English teacher want to burst out and scold the offending person.
Yes, 5a and 5b are interchangeable.