Forget whether or not to put your keyword in it, make it relevant to a searcher and write it for humans, not search engines. If you want to have this 20-word meta description which accurately describes the page you have optimised (for one or two keyword phrases) when people use Google to search, make sure the keyword is in there. There is more likelihood it will be used by Google as your snippet description in SERPs.
Link text is the visible text inside a link. This text tells users and Google something about the page you're linking to. Links on your page may be internal—pointing to other pages on your site—or external—leading to content on other sites. In either of these cases, the better your anchor text is, the easier it is for users to navigate and for Google to understand what the page you're linking to is about.