the fx5500 runs dx9 in theory. However when you play games with it, it does not run direct x 9. I believe the 5500 goes direct x 8.1.
No, if you have direct x 9 installed on it you are fine. You shouldn't be getting frames that low with that system. My downstairs system is a p4 2.4 ghz with an fx5200 and I get pretty good frames on low.