I think I've been there once or twice, at least, and yes, it is a bit of a catch 22. Have you tried any sleep aids? Melatonin is good and is supposed to help protect the brain against mercury. Also, I use Calms Forte homeopathic formula, and L-theanine and l-tryptophan, both calming amino acids. When it is really bad, I bust our the xanax. Your body really needs sleep in order to heal!
Have you thought about sauna therapy as a way to detox mercury? You sweat it out through your skin without stress to your liver, kidneys, etc. I bought a portable Far Infrared Sauna for about $350 and it is great. Also works wonders for candida die off, joint pains and menstrual cramps! You can also do clay footbaths to take out mercury or homeopathic formulas. AND I also recommend acupuncture. If you can find a community acu clinic in your area or an acu school, it can be quite affordable. Good luck!