R.J.
As a shot in the dark (because I'm not familiar with all the methods that are used for colic), have you tried marathon burping after every feeding? Aka... don't stop at the first burp, but continue to pat upright for 45 minutes - 1hr until a monster burp -or a gazillion little ones? (I got good at reading a book one handed).
It just strikes me that if he's absolutely fine when you're out and about (with lots of vibrations and up and down movements that may be moving the gas up), that you might have a marathon burper.