You said ' "a few" or "a little" means the feeling or opinion is neutral, on the other hand, "few" or "little" means negative feeling......so my answers are better.....Am I correct?' No, I'm afraid that you're not correct, and your answers aren't better. Your answers to 1 and 2 don't make sense, and your answer to 3 is wrong (you can’t say ‘very a little’).
The difference between 'a few'/ 'a little' and 'few'/'little' is not necessarily about neutral feelings or negative feelings. If that is what you have learnt, then I'm sorry to say that you have been mistaught. Depending on context, any of these words may have negative or positive implications. For example:
I have a few friends = This is a good thing ( I'm not entirely alone )
I have few friends = This is a bad thing (I don't have many friends)
I have few problems = This is a good thing (My life is relatively unproblematic)
I have a few problems = This is a bad thing ( I have a number of problems)
In fact, the difference is this:
few/little = not a lot
a few/ a little = not zero ( 'some')
Let's look at the first of your sentences:
The answer has to be 'There were few people', meaning that there weren't many visitors and the museum wasn't crowded. 'A few' would be impossible in this context: 'There were a few people' would mean that the museum was not empty, which makes no sense in the context of the rest of the sentence 'so we could see everything and there were no queues'. (“The museum wasn’t empty of visitors, so we could see everything” is nonsense).
An example of a context where ‘a few people’ would make sense would be this:
"The museum owner wanted to close the museum early and go home. But she couldn't do this because there were still a few people there. She waited until they had gone and then she quickly locked the door'.
In this context, 'a few' is correct, because it means that the museum wasn't empty (remember - 'a few' means not zero).
I hope that's clearer now.