Hey there,
Google works hard to recognise misspellings and place the most relevant website at the top of the search results. So the first thing I would look at is where you are actually ranking for those misspellings and secondly, how many searches are there for those terms each month?
To most accurately achieve this, I would run an Adwords campaign using exact match on all the possible misspelling combination, setting an unlimited budget and then measuring the amount of impressions generated. Make sure it is exact match or you will be left thinking you've struck gold, when in fact you have erroneous data.
If you do really want to optimise for this term and you are not coming up first for that term, then I would look below the onpage factors. As I said, Google's pretty dang good at picking up typos, so instead I would focus on improving your link profile so you are an authority on the area. Also creating more deep content and internally linking through to that one central page will help to channel the link juice through to that key page.
There are some that will argue that misspellings on your website look terrible and devalue the brand. To avoid this I recommend focusing on the linking side of things and only onpage typo's if you need to. If you do go down this path, then create a new page and link it in through the sitemap so that the vast majority of your customers are not exposed to the typos and put off your service.
2.) Check the settings for the on-page optimiser and the most recent cache date, both of these could be throwing off your results. Also, make sure you have your computer set to private browsing. One thing Google and Google + are doing now is looking at your history and automatically increasing the rankings of sites you visit regularly.
OK, that's enough of an epic answer for me. Hope you like it
Josh