Natural sources of calcium include bone meal and dolomite, which may be contaminated with lead. Calcium carbonate, a laboratory creation, is the way to go. Vitamins and minerals play key roles in every body system. So, yes, they're involved in all of the above, and more. But by themselves, supplements won't turn around your life.
Chelation combines minerals with other substances, usually amino acids.
Proponents claim that chelation promotes absorption, but the evidence is scant. The body breaks down the protein into amino acids. Forget brand names. A small number of manufacturers supply all the companies that market supplements. Ten dollars a month should do it.