You've got excellent vocabulary and grammar (just a few little issues here and there). However, your essays lack structure. You should be following a basic Intro/Body Paragraph/Body Paragraph/Conclusion format. Fortunately it only takes a short amount of studying to learn that.
Seriously, if you follow a traditional structure and maybe length your essays a bit you'll earn a very high score in the writing section of the TOEFL.
The link in my signature does include a guide to essay organization (check the "writing" section).
:TOEFLresources.com: Step-by-step guides to the test and a free essay evaluation service