just don't rely on third party tools and come to decision mate. add good content, build quality links and go on. nothing will stop your site.
no.. sandbox means all your indexed pages wud disappear and a penalty is a negative push deep throwing your site way back in serps for doing something against Google ToS.
Where do you get this info? With the sandbox effect your pages are still indexed but the are not ranking.
Actually from the traffic, you will know. If there's no traffic from search engine for one month, and the website is quite old, then there's something very wrong.
Sandbox effect is noticed on new websites too. In this case its not a penalty. But yes Google can slap the sandbox on sites that are spamming, into link exchage networks solely for the purpose of ranking in search engines.