On the FTF, did you try a second strike to see if they fire? I'm wondering if the primers aren't seated enough.

On the brass filings, something isn't right.

How are you lubing your bolt carrier group? Initially, you do want to run the rifle wet for while, though ARs in general tend to prefer to be run wet than dry as a general rule. After they have been used for a while, you can lighten up on the lube if dust and dirt is a concern. As far as the number of rounds, 200 is a good number but like ammunition brands and loads, every rifle is different as to what works best for that particular rifle.