If I understand you correctly, you are thinking of spending big bucks to install a liner in your well because you don't want to set the chlorine dose high enough for the max iron content in your water and leave it there so the equipment will work, you'd rather adjust it up'n down to save a few bucks worth of bleach.
And you're justifying do that by now wanting to get rid of chemicals.
Question, say you do that and you cut your iron content in half. What are you going to do about the acidic water and is your softener capable of removing the iron with good salt and water efficiency?
BTW, a 5" liner seriously reduces the clearance for and volume of cooling water around your 4 inch diameter submersible pump. And if the pump overheats it can weld itself to the PVC. You also lose a lot of water storage in the well.
I use chlorine for your type water but I don't use a solution feeder for bleach or soda ash to raise the pH. I use an erosion chlorine pellet chlorinator and a backwashed acid neutralizer filter. And I would not use alum. I don't use large retention tanks, I use a bottom drain 12" x 65" tank with a patented mixing feature that is equivalent to a 120 gal retention tank; that usually does not have a bottom drain to get rid of 'sediment' build up in the tank.