981 posts on my passive blog, should I delete some posts for SEO?

You can archive the posts but I wouldn't delete them. If you know that some of the posts haven't had ANY hits, you could delete them I guess, but deleting posts won't help SEO. Each page has it's own ranking.

Since bdenzer has already answered your first question, I'll answer the second one.

Sorry, no free software. Even if one existed, it wouldn't be accurate enough to be relied upon. The best way to evaluate keyword competition is manually analysing the top 10 sites ranking in Google for your keyword and their link profiles, and you don't need a software to do that.

Yes I delete them and leave a few with good back links so you can freshen up the content for seo ,If your blog have many oraganic backlinks ..So i think dont delete this blog ...

Don't do it!!! You would be crazy to delete your old posts and with that your hard work down the toilet... Those posts add credibility to your site... as well as a great index count....

I'm a little confused why you started a new site with redirect from the old one? If I was to do that I would have also migrated the old posts and used the canonicalization tag on the old site so that the link juice credit would flow to the new site.... and/or redirect those pages/posts mapped to the new location via .htaccess file...

As you have now gone back to your old site... Then the first thing I would do is amend each post with a revised date - assuming that the content is still relevant... You could add an opening sentence last revision date XXX - and perhaps add some additional changes... Also keep adding new content and look into building silo's with building internal links within your site which leverages the 900+ posts and hopefully when G comes crawling again it will begin resurrecting your old site...

Hope that helps and good luck ;-)

Thank you. I think I will keep the posts and freshen up the ones with backlinks.