It was far too painful to try and read all the posts in this thread.
However, the OP was asking about detecting in Iron Infested areas.
As a new student of metal detecting I have tried to read all available, factual material I could locate and I think these articles may help. Even though they are quite dated, the technology remains basically the same.
I suggest reading them in this sequence and they may give you some ideas on how to approach your detecting situation.
http://www.dankowskidetectors.com/behindthemask.htm
http://www.dankowskidetectors.com/painful_truth.htm
http://www.dankowskidetectors.com/irondiscrimination.htm
HH & GL