I also agree that root canals are EVIL. The microscopic tubules within the root get invaded by parasitic fungi which spread through circulation whenever you chew. Get them out ASAP, the entire teeth and the connective tissue/cavity inflammation that the dead teeth are embedded in. I would NOT chelate before this is complete, because the dead tissue of these teeth may also dissipate Amalgam and cadmium. Your broken bone is the result of the cadmium that is inherent in the substance they call Gutta Percha, a "plant-derived" (what a scam) sealant that is put into the root canal after the procedure to supposedly seal it off. Well guess what, it leaks cadmium and God knows what else. Get these dead teeth out, they are only trouble and may give you cancer (I had melanoma on the meridian of one of my root canals that was leaking, twice, I almost died from it; I only had six teeth with root canals, but performed repeatedly. I can relate to your story).
Regarding your question: it depends.
I've been chelating on the Cutler protocol for close to seven years now and built up my capacity to 200mg Alpha-lipoic acid every 3 hours (the only brand that works for me is Dymatize Nutrition). I know, that's a lot. I don't get symptoms anymore UNLESS I screw up the protocol. I am still toxic, but getting better. Iris analysis helps me to track my progress without lab tests (my eyes are light-colored so you can see stuff without any special equipment; a smartphone cam helps occasionally). Based on this and my current symptoms I believe that my brain is pretty much functional in terms of the control of hormone production. This is the key to fasting. You can't fast when your body is a total mess running on adrenaline (see the Cutler book for information on the inappropriate ACTH response to stress in mercury poisoning).
Back to your question: Can you do a water fast? Yes AND no! If you react to a workout the way you described, you will do more harm than good by skipping food. Also, you may cause a MASSIVE, and I mean MASSIVE, die-off of Candida and the likes in your gut. I recently experienced this first-hand when I went on a Water Fast using some spectacular mountain water (Pedras Salgadas, the only water I know of that is sparkling by nature). Well, I felt better, until about three days into drinking the mountain water--which is healthy, mind you--all hell broke loose in my body. I am pretty tolerant to pain, having gone through all the surgeries I went through (some WITHOUT any anesthesia, don't ask), and let me tell you, the pain of this event was pretty much in a league of its own. It's like Fibromyalgia only MORE intense and non-stop. My muscles felt like they were tearing off of my bone and off my joints for two days straight. I was rolling in bed, walking back and forth, crying, praying, screaming, couldn't sleep for a minute--I got to a point where I basically wanted to shoot my legs off. Then the pain suddenly disappeared in a matter of minutes and only the brain fog lingered. I felt genuinely drunk (classic Candida). When my head cleared the next day, I realized what it was: a die-off of fungi in the digestive tract, brain and elsewhere (fungi are a big part of Fibromyalgia if you ask me, courtesy of the root canals they told us were "safe"). You can't think straight when this is happening. You need someone at your side, a friend or a spouse, who understands what's happening to you, and will keep you from doing something stupid.
Yes, these fungi are bad, but there is NO WAY I would have survived this event a couple of years ago, with the Depression I had and the debilitating adrenal fatigue that's affecting most mercury-toxic people.
IF you want an advice, here it goes: be gentle to your body. Trust the Creator to fix it for you, NOT the medical system (it's a devillish scam). If you need to operate (as in: hold a job that pays your supplements), take bioidentical hormones, NOT synthetics, until you get past the worst part. Supplement wisely (I take Garden of Life, food-derived vitamins, but not the protein powders. I found the absorption is best when they don't add toxic chemicals and this is about the only brand I could find that does _not_ cheat with nasty additives like magnesium stereate/stearic acid that will wreck your gut if you take it).
My answer to your question is: wait with the fasting until your adrenals kick back in.