Hi Andy,
First thing fix all of those errors and as many warnings as you can. Those typically are affecting your ranking, as well as your user experience, so those should be worked on before anything social or content related - in my opinion.
Also, my suggestion would be to think big, but start small. It sounds like you have a lot of great ideas for going forward with the website, but I would recommend that you focus your efforts in one area and master it... I mean really knock it out of the park. For instance, if you have Facebook, Twitter, and LinkedIn, instead of engaging half-a$$ed (which I'm not saying you are, I am just saying that managing 3 social media accounts can be WICKED challenging to do right in addition to everything else you are taking on), really focus on one - whichever is bringing you the most traffic or engagement and really dominate in that area.
If you are a one-man-team trying to accomplish all of this, you may be spreading yourself thin in trying to tackle all of these different areas, that's why I suggest going after one area and once it is really rocking and it only needs a bit of maintenance, move onto the next - I fell you'll see a bigger return going this route. But, if you have a whole team pushing the website, I think you are going in the right direction.
Good luck.
Mike