Sorry about the blog vs website confusion. IMHO, promoting a website is better.
When you say 17,000 indexed links, you mean G is showing 17,000 pages for your site? And it's only PR3??? If so, something's wrong.
Or are you saying that G shows 17,000 inbound links? If that's the case, 20 PR6 blogs aren't going to sandbox your site. They're hardly even going to make a dent, in the sense of doing something harmful to your rankings. With a site that big, they can only help. So if your rankings are plunging, something else is going on, something unrelated to the blog articles.