When Violet says, "it makes good times even better when you know they are going to end"; what does she mean? Do you think her analogy of grilled vegetables being better because some of them are partly soot a good comparison in this case? why or why not?

You have quite a few questions here. Generally, Violet means that life is always subject to change. Good times have to end in order for harder times to happen. There are no "good times" if one has never experienced "bad times". We appreciate the good times because so much of life can be difficult and challenging.