Honestly, the sandbox isn't something Google is doing much now. It was more something they did several years ago before they had the power to quickly crawl and index new sites. You say your site has been indexed - you used to rank for your target term and you're still ranking for other terms. That means you are not in the sandbox.
Again: you are not in Google sandbox. If you were, your site wouldn't be in the index at all.
It sounds to me like you're not ranking for this term because it's very competitive. The link sources that you mention (squidoo, article marketing, press releases, directories, social bookmarking) are all relatively low-value. I would suggest creating some new content for this term. Take a look at the pages that are ranking well for the term and figure out how you can provide a resource that is different from them while still being useful. Then try to get some links from related sites - maybe doctors, medical/support communities, pharmacists, etc. The best way to do this is to create a resource that would be useful for these target audiences and then reach out to them to see if they will link to or share it.
Ranking for a very competitive term is hard and takes a long time, and a ton of work. It can definitely be done but you may also want to see if you can rank for less competitive, more specific terms - like "homeopathic hemorrhoids treatment," "hemorrhoids treatment over the counter," etc. This would probably be faster and you would need to get fewer quality links to rank.