How many Power Feeds do I need for a 30' run of track?

The number of Power feeds required depends on the load, and not on the length.  The track is able to accommodate 20 Amps, at 80% capacity, i.e. 16 Amps.  That works out to 1920 watts maximum. If you are loading more than 1920 watt on the rail, you will need a second power feed.