Toyota Repair: 02 Avalon lower pan drain plug, silicone sealer, main bearings

Question
Recently purchased an xls 3.0 L 6 cyl. 4 door sedan. Pulled drain plug to change oil...plug is self taping M12 1.75. Metal cuttings still in the plug center and in the oil. I have flushed and changed 3 times. Had compression checked...4 cylinders @ 175 psi 2 @ 170 psi. Two questions:
Is there any other tests to determine condition of motor, e.g., is there a way to check main bearings (bushings)condition?
Is there a drain plug size that will not leak?...tried regular m12 1.75 plug but is very loose...still using the self taping plug which leaks slowly.

Answer
There is no way to check the bearings without removing the oil pan and then the bearings. The compression is good. Use a gasket on the drain plug not a metal sealing ring, you can also apply a coat of a silicone sealer to the plug until the next oil change, as long as the plug can be tightened it should be ok, the other option is to replace the oil pan.