i think they have lead testers on the market, but some i hear are confusing. see if your county has any resources for you, as any day care provider licensed through the county would have to have these resources. i am a licensed day care provider, but my house was built in 97, and so they didnt even talk to me about lead.
why are you worried about iron? you should be more worried about fiber, which actually HELPS the body absorb and use iron. fiber fiber fiber! this may be unknown, and actually the opposite thought may be the popular one, that fiber blocks iron, but it does NOT! trust me on this. :D this is almost like the cure all for so many many many issues in this country, if only more people knew about it, constipation wouldnt be a household word!
what you can do about it is simple. buy a box of milled flax seed. sprinkle some on cereal, pancakes, sandwiches, yogurt, ice cream, pretty much anything. it is a little grainy, but basically has no taste, and adds a GREAT nutrient; fiber! :D its the best thing that ever happened to us :D you dont need much, and you can adjust the amount, if it doesnt work, use more, if you get too watery stools, use less. but about a teaspoon works well for just about anyone.
www.thechinastudy.com is a large study - they released a book in 2006. it compared diets of americans and of chinese, and found out many many diseases we have in this country are absent in china and it boils down to differences in diet! hard, chunky, stiff, painful stools are usually caused by only a lack of fiber.
see, we dont digest fiber. however, it is important to know that fiber absorbs water in the stomach. then it holds this water as it goes through the intestines, making stool softer and easier to pass. the way it should be! this simple addition to diet prevents not only constipation, but hemmeroids, fissures, and colon cancer! this goes against most doctors in our society, but the research is amazing!
as far as the lead, im not sure what to do on that. if they say more iron, then try that in combination with more fiber!!! i cant believe that they want to wait so long before testing your son again!
what i do know is that fiber can also helps flush the system, maybe with an increase in fiber there will be a decrease in lead. thats a tough one because lead tends to stay put. give more liquids, especially water, and some flax seed, or high fiber fruits, vegetables, etc. WHOLE GRAIN BREADS, not enriched, not bleached, not unbleached. WHOLE GRAIN. try to find a bread without syrups too. (sugars). if they are too expensive, try making your own with whole wheat flour or try the local farmers market, or find someone who makes good bread to trade with...
anyway, good luck