I would get more thorough testing done. Interesting that you have iron AND chlorine. With only 7 gpg, you can get a very high efficiency system and use very little salt over the years.
If you are spending $30 a month on bottled water...wow. You can do much better by getting a quality RO. No wasted bottles, no shopping, rarely would you run out, use it for plants, pets, steam irons, etc., that you don't use bottles for. Also, you have better control over quality; who knows where the bottled water comes from.
Andy Christensen, CWS-II