When I'm doing keyword research, one of the first things I do is go on competitor websites and see if they have the meta keyword tag. If they do, then it instantly gives me access to all the keywords that they're targeting and allows me to work on beating them. Deleting your meta keyword tag prevents your competitors from doing this to you.

You can demote sitelinks so that they are less likely to appear but Google displays the pages that it considers to be most relevant to the searcher. Use the Mozbar to have a look at what the PA of the pages displayed are compared to the ones you want to display. You may need to have a look at your internal linking structure to improve the authority of the pages you want to display.