The skin problems may be liver related, a few good liver flush and then keeping it flushed daily may do wonders, if all else fails a liver tonic may snap him out of it.
The root canals and mercury, yes, he has a hard road to travel. It cost more to remove the damage than it did to cause it and some teeth are dead and will be toxic the rest of his life. I suggest the teeth be priority one, start on a few each year until he is metal free and free of all root canals, etc. as explained in clark's advanced cancer book or a hall huggins book. I also sale a dental book that explains the health great, but the laser method it explains is the most expensive.