Yes, a blog with respect to the subject that you are writing about assuming it can be authenticated with a proper foundation can be used as evidence with respect to any matter, civil or criminal.With respect to what you have written as the subject of your question, I recommend that you consult with a criminal defense attorney about the accusations against you sooner rather than later. Possibly there might be some admissions by your former employer in the blog that may assist you in your defense to his accusations.