During break in a little fuzz on a magnetic plug is ok. After break in any steel or iron is abad thing. If you have enough that you can pick it out and take it to somebody to show you've got problems. While the bronze colored particles could be from the valve guides or wrist pin bushing if you have bronze guides and or floating piston pins most likely the bearings are excessively worn.
You can put the screen over the filter and check after an hour of running. If you find nothing check the screen every few days. You can put the filter back on if you don't damage it or the filter gasket removing it. Keep in mind that the more you stroke this along deciding whats wrong you might be chewing up parts that would have been rebuildable had you pulled the motor at the first sign of excessive metal in the oil.