Be sure that you’re not doing too much to fast. You don’t want the little things to break your body down. Speed is great early on. However, be sure your fitness level is high enough otherwise you might meet you goal paces and your body may not be prepared for such work.
I see that you are going to train 200/400 like different workouts? I don’t really see a need for that. I think you can develop your speed for 200 by doing 400 workouts.
Another thing, vary your lifting workouts so they aren’t repetitive week after week. What will you SE workouts look like? How about your lifting plan? Give us some examples, it might make it easier for 400, etc to help you out.