If it is running hard against the BB sprocket guide plate the screws will eventually fail and the guide plate will come off. The belt can touch the tyre sidewall or shock absorber if you start to run to the extremes of adjustment. I think any adjustments with a worn alloy sprocket will only be a short term cure. You have done well to keep the alloy sprocket for 11,000 miles, it's usually less than half of that before worn out.
A silicone spray sometimes helps quieten things for a few miles but the real cure is a new sprocket. The belt is usually fine, even after shredding an alloy sprocket. Give the belt a wash with warm soapy water the get the debris off it when fitting a new sprocket, there will be a lot of black dust about.
