Russell, how long is the 0% period? If the 0% is good for another 6 months, then as long as you can commit to paying it off before that interest rate changes, you're OK. It's costing you nothing to keep a small balance on the card. Whatever you decide to do, just make sure you pay it off or pay off as much as you can before the 0% introductory period ends (someone already mentioned this).
FICO scores only go up to 850 and many many many lenders use FICO. I've never come across any financial institution that didn't use FICO scores.
As for the other arguments, debt-to-income really is a big deal. The higher your DTI, the lower your score.
And 750 is a good score if you ask me. It's hard to believe someone who is 20 having a score over 800, but I've seen stranger things. Just to give a quick example, most of the loans for vehicles that are advertised as 0% interest are usually reserved for Tier I status, which is usually scores over 700 and is described as excellent credit.
