There is nothing wrong with what your doing, but its sure is an unefficient way to stretch.
If you go to www.stadion.com/column.html
you will get all the info you need.
but long story short:
Be able to squat your body weight easily for 10 repititions. Deadlift once or twice with double your body weight. Once you can do this practice lunges with weight (side and forward) adductor pull downs and run regularly taking big long strides preferable on soft ground such as a park.
Morning - 10 mins dynamic stretching
Pre workout dynamic stretching
Post workout isometric strething followed by relaxed stretching (you can just do relaxed if your legs are too tired).
Dont do the isometric stuff until your body is strong enought i.e. the squats and deadlifts.
If you can already push this kind of weight and you run regularly you should be able to get into a full split very quickly. If not get strong then get flexible!
The dynamic stretches will enable you to kick high anyway so it is better to concentrate on your stength and dynamic flexibility before working on speicfic strength work for splits.