I had IT Band issues leading up to Dopey. While it is too late for you right now- afterwards you might look into dry needling. (google it in your area) That really made a HUGE difference for me running Dopey- I ran pain free after 3 treatments. But it was inflamed afterwards and I needed a few extra treatments to help it heal overall. I could not have completed Dopey without the dry needling!
During the race you might try some BioFreeeze- at the aid stations. And Dr. Cool has a great knee wrap - at the expo.
My ITBand strap like others was just OK. The compression sleeve felt better- but I would save that for after your run.
Check out some yoga for ITBand- those stretches might help a bit too- the night before and after your run. Love this video!
IT Band issues are symptoms of weak core muscles and being quad dominant- you need to look into cross training to improve the base problem. (Me too!)
Take care of yourself and enjoy!
PS: You might want to look for another doc that provides more insight than "runners knee" . Having someone that understands running/sports medicine can make a huge difference and might have helped you more ahead of time.