I agree that an increase in dose does not seem wise.
Mg is one of the essential supplements while chelating with Cutler. It definitely can help mood for some, including a close friend who is chelating. More on this in the Files of the frequent dose chelation yahoo group & Cutler's Amalgam Illness book.
When people are pushing doses too much they often get an increase in low adrenal symptoms. I think this is part of what you are experiencing. I've seen way too many reports of this. Are you getting adequate adrenal support?! If you are not careful you'll be like lots of others who crashed their adrenals or something and had to take time off to put the pieces back together again.