Hi eanik, and welcome!! Just wanted you to know that I learned how to maintain my pool using TFP methods with the same pool as you have. First 2 years were a disaster until I found this site. So you're 2 years ahead of me in that regard!!
Also, my daugher has exzema, and she goes through torture when she swims in friends pools or a public pool. My pool is much much better on her skin. Adding an SWG is a great idea, but even if you didn't do that you could still add salt. It softens the water, and her skin just feels silkier when she gets out. Also, I added borates to my pool, and that seems to have a positive effect on her skin also.
I noticed you mentioned that you want to "keep it mild" for your daughter's skin. I'm not sure exactly what you're referring to, but when using the proper level of chlorine for the CYA level, you're water will be "milder" than a pool with no CYA. Even though a chlorine level of 6 or 7 ppm may seem high, it isn't when you understand that the active chlorine in a properly maintained pool is less than .2 ppm (someone correct me on that if I'm wrong - I'm recalling it from an old chem geek post). This means that a chlorine level of 7ppm in a pool with a CYA level of 40 would have less "active" chlorine than a pool with no CYA and a chlorine level of 1 ppm.
I may be wrong on the numbers just mentioned, but one thing I can assure you is that my pool water is better on my daughter's skin that any other pool she has ever swam in, from Newfoundland to Florida. And it's all thanks to TFP. Trust the experts here (of which I am NOT one!!), and you will have an enjoyable, safe, easy to maintain pool. Good luck, and please keep us posted. I'm interested in how your daughter's skin reacts after you get all your levels in order.
P.S.
For what it's worth, when I had that same pool, I used 2100 gallons as my volume. Seemed to work fine. Test results matched what Pool Calculator indicated.
GC