Here is one thing you will find useful.
I am thinking that with <.2 mg of iron, I am a little surprised that the coloration in the toilet would be much. It's in the tank too, right? Iron Out is good for iron stains.
Read through some of the earlier threads, and some people will have some more info for you. Consensus is for separate resin tank and brine tank. I suspect you have read some of those.
Are you on your own well?