If I read correctly, your ranking has ranged between page 2 and page 6, correct? Because if so, the difference between ranking between page 2 and page 6 is minimal. It's only when you break into page 1 and the top 5 or 6 slots that you can consider your SEO strategy a success and can start thinking of more ingenious ways to crack into the top 3.
Page 2 is not a successful SEO campaign, and I say this simply because I am tired of seeing SEO sellers promising the moon to newbies only to leave them on page 2 and the sellers brainwashing the customer of how well the SEO campaign has gone. If you are on page 2, you might as well be on page 6 or 10.
1) sandbox for new site (1.5yrs old re-registered side from 2007), and play the google dance?
2) not enough nofollow links? has 2 domains out of 60 pointing nofollow links
3) some users have said in other threads to build some social links to point social signals. Is G really giving it that much weight?
1) There is no such thing as a sandbox. This is mere SEO fairy tales invented by people who claim that nofollow has a direct effect on ranking or who think that Wikipedia links give you an SEO advantage.
2) No you do not need more nofollow links. If anything more nofollow links will make you look like a spammer in Google eyes.
3) LOL social media does jack absolute ZERO in improving rankings or anything to do with SEO. Zero, zilch, nada. Do you think that Google is going to care about a nofollow link on some fake facebook profile of a fake user who has also liked Mike's Gardening supply store in Newcastle (UK), Vishal's dj hiring agency in Delhi and Joe's private drug rehab clinic in Orange County (USA)?
What you need are real links from high authority sites on pages with high PR scores. Otherwise you will never move up, unless the guys on the first page are demoted from either an algorithm update or a manual review.