Having some articles written to post on our site and once indexed by google will submit to a few directories. My question is, in my links from the article back to the website should I link to the article url or homepage or any other relevent page?
Link to the most relevant page. If you don't have one then link to your homepage. BTW, Don't submit articles that already posted on your website and Vice versa.
Yeap. As rule each page is optimized for certain keywords. Better link to the same page with the same keywords you used in the article
Yup,it's depend the necessary page that you are working on.internal page also help increase the PR for homepage.