where can I add my LinkedIn link in my expert profile

The most important thing to understand is your audience, or rather your target customer. In the beginning, it can be a bit overwhelming to all of a sudden tackle half a dozen social media platforms and do them all well. Focus on just one or two platforms where you know your ideal customers are. For example, if you're building a saas product for techies, get your butt on Twitter and engage with anyone and everyone who's commenting on related hashtags or other Twitter-ers. Twitterites. If you're producing high-end physical products that look awesome in photos, post daily on Instagram and get people to oogle at your Instagram feed. Of course you should still claim your business name on all the platforms just in case, but focus on a few. Use tools like Hootsuite, MeetEdgar, IFTTT, and Zapier to help you automate some of the posting process. Just don't cheap out on your content ;)

I think you can be charging much more than you are, but if you're working with smaller businesses then maybe that budget is more reasonable. Why not offer some kind of tiered option? A post is $15, highlights are $10, but if you get both they're $20—something like that. If you other avenues to distribute your news (like a newsletter, for example), you can add additional packages. I also think 3:1 is too many ads but if your audience is still engaging and there isn't a noticeable dropoff, that's not too bad.

I work extensively in the healthcare market. In particular I have quite a bit of experience marketing to MDs and other healthcare providers. And in my experience - that audience is not likely to be reached via social media. Medical professionals (particularly MDs) are mainly offline. Online business related activity is generally limited to reading journals and correspondence with other medical professionals. In fact - they have such a huge "target" painted on their back that they are very challenging to market TO at all. This is not to say that you can't be successful in working with them. Only that if you "target" them you're likely to get stonewalled. I'm curious why you are intent on reaching them in this manner (i.e. social media)? One of the main tenets I teach my coaching students is to find out where your market is... Not to choose a form of media (i.e. twitter, FB, etc) and hope to reach them there. You may have greater success (and waste less time/money) re-thinking your business model. I can certainly help with this if you decide to go in that direction. In any case - Best of luck!

It's far less important than it used to be, because so many social media businesses are much more reliant on their apps than their desktop websites these days. Instagram launched (and grew fast) with the domain instagr.am, for instance.

I am not sure of the specifics you're asking, it seems like a lot of technical data. This might help in your search for these statistics though: http://jobsearch.about.com/od/networking/a/linkedin.htm http://www.forbes.com/sites/nextavenue/2014/01/21/how-linkedin-is-thwarting-your-job-search/ http://mashable.com/2014/06/19/linkedin-job-search-app/ http://www.cio.com/article/2403150/linkedin/10-linkedin-tips-to-boost-your-job-search.html