As for a probiotic, look into finding a brand by UAS Labs called Probioplus DDS. I'm not sure where you can find it. I know Vitaminshoppe.com carries it, but it's backordered right now. They guarantee that the strains will survive the trip to the gut. See link below. Also if I'm not mistaken that brand of iron supplement has 2 kinds, one has yeast, the other doesn't. Make sure you buy the yeast free one. See link below. Also the reason you need to use it up so fast is because it doesn't contain preservatives .
Are you sure you really need iron? I've heard that you should be tested to make sure you really need it or it can be toxic. Hope this helps.