2.63 mg/l will convert all ...

2.63 mg/l will convert all the chlorine to chloramines which is poor at oxidizing Fe. The amount of cl2 required to break point chlorinate will be too expensive. While less cost effective a better strategy would be biological filtration with nitrification - denitrification and biological iron removal at the same time. The expensive part is getting enough dissolved oxygen to convert that much ammonia.