Complex question... let me offer the thoughts from my mind...
1) Don't run to the beat of a song, very likely to push you harder than is sensible...
2) Rumour has it that if you breathe with a certain rhythm of running i.e. breathe in when your right foot hits the floor, you will get stitiches or cramp. breathing rate and running speed should be independent, not that I can tell whether this is true or not...
3) Depending on what type of running you are doing, it may be a good idea to running speed on a point whereby you can talk comfortably i.e. you're not choking for air...
4) In through nose and out through mouth wont cut it as you get faster, it doesn't matter so much unless you are running next to a dual carriageway