Let me clear up some confusion about medicine in general: Unless you have are about to die or have a visible condition like a broken bone or something blocking a blood vessel, when instead you have a "fuzzy" condition, no one at all will be able to tell you in advance what he results of taking X or Y will be. When you're lucky there are statistical statements - x% of people with a condition like that experience this or that, etc.
When you ask about chelating and mercury, however, you are on the farthest end of certainty possible! So nobody can answer your question.
What you do: Do you have a reason to suspect mercury could be an issue (apart from your test results, they don't mean much)? If not,... well you get the point.
If you have reason to be concerned about mercury the only way to know if a chelator would help is to TRY IT. With "try it" I mean regularly using it for 3-6 months, one-time experience, even if positive, is not a clear indicator - unless you have just experienced an acute poisoning, which usually happens in industrial settings only. Because many chronically mercury-poisoned people won't feel much the first few times, and if you do feel something it could be a psychological placebo effect.
And about "reference ranges": Forget it. Watch some medicine lectures, it's all on youtube these days. Doctors use blood- and other values only IN ADDITION to a lot of other tools, by themselves they mean NOTHING, unless they show extremes in which case the extreme will have to be treated (if it's life-threatening).
However, the nice thing about mercury test results is that while they are useless when they don't show anything, when they DO show significant mercury than it's pretty certain that you HAVE considerable depots, unless you were just exposed when you performed the test and otherwise not.
Also to consider in your case - lead and mercury: There is a thing that the toxicity of several poisons can be orders of magnitude higher than that of any single one of them. Lead and mercury are in that category, together they become about a 1000 times more dangerous than either one by itself!
So DMSA would be a good choice, because it chelates both metals pretty well. For mercury alone DMPS is (a lot) more effective, but DMPS is not very good for lead.
If you have no significant burden (of mercury and lead) than taking a chelator will have no effect, should you experience problems it will be a(nother) sign that you have a problem, and also that you've chosen the right treatment.