be careful using this though, Japanese are traditionally modest and view self promotion as a form of deceit. Just teacher on a name card would be better than education specialist
Unless you're feeling extremely pretentious, exactly the same way you always have. In some contexts it may make sense to append the abbreviation for the specific degree, but outside of a formal...
It depends on where you graduated. There is a number of abbreviations for a master's in education - once again - depending on where you graduated from. Common to this field are the following.
M.Ed....