FDA does set guidelines that need to be followed although they aren't necessarily as rigid as guidelines for pharmaceuticals. FDA regulates food too, so herbs at least have some guidelines. Yes, I've used it before, it seems to be very successful for some patients. However, vegetarians do not like to use it. For a supplemental form, Ferrous Sulphate is good but give it on an empty stomach if it is tolerated.
Estrogen tends to make fibroids grow, which is why they tend to shrink after menopause.
Typically, processing includes a purification process. Again it depends on the company. Can you mix tintures with anything. I have some problems with the taste. Yes, you can mix it with juice.