Well...it was not good that you broke it in at 30 degrees. The purpose of the break in is to heat metals, let them expand, then break them in by rubbing against each other for smooth operation. Since it was 30 degrees outside, i think the engine was a bit cold
I would tear down the engine, and check for compression and proper fitting. As for the shavings, take a look at the bearings, they are known to go fast in these engines (I have a Hot MOD version of the N21BF), and if it needs it, give the engine a rebuild. Nova suggests a full teardown of the engine after the first four gallons, by then the engine should be properly broken-in.