Thanks for your feedback, so I'm not the only one with this defect...I'm not sure what you can do to remove it. I had the exact same issue with mine, so I know what you're talking about. The lapels had an odd white reside/powder, that continued to flake down across the rest of the suit while posing. I contacted Sideshow and will be shipped a replacement.
It is an horror...You can try using some putty, to try to remove it perhaps, but I've never tried it.
I agree with keeping it battle damaged. He's in intense fights the whole movie, having a pristine jacket is actually less accurate. With all the wrinkles in the clothes that'll happen in any pose, it's likely not an eyesore