I have been having difficulty with softer (volume wise) playing, especially on high tones. My air stream seems to die on me when I attempt soft playing and my intonation goes haywire. Does anyone have any advice to help me improve me softer playing?

Lower volume only means that LESS air is being put into the horn, not slower air. Make sure that slower air isnt vcoming out.
It's hard to play high and soft.
It's something you ought to work on yourself, or get with a private teacher

Make sure you are using your diaragm to blow the air throw your horn. Push the air out of your lungs using your stomach, not your chest. That could be your problem. Playing softer helps to build your lip muscles. Also, make sure you are sitting/standing properly when you play. Hope this helps.