I link internal articles, they pass the QAP swiftly. I'm not sure if there is a limit to internal linking, but I have read the articles of experienced Hubbers who have several internal links.
Linking to Wikipedia is not essential. You must be already defining about that subject/topic in your article. I believe it's covers enough that way.
Besides, everybody knows Wikipedia. When in doubts, and when they need more information, people are smart enough to use it without your having to give them links.