working in the industry, I help a lot of people with this issue. Pool startups are difficult to go pure softened water. The benefits are there, but if you are building a plaster/concrete/marsite pool, then you do not want soft water... at all. A vinyl, or fiberglass pool, then you don't need calcium at all!! Iron obviously is not desired (along with manganese) De-ironed water, try bypassing just the softener, but be mindful depending on what type of iron filter system you are using, most like softeners have a maximum gallon capacity before they need to clean/regenerate/pause. So if you are still wanting to use the softened, de-ironed water, then you will have to do some calculation... need to know the general hardness of your well water, (preffered in grains per gallon, so take your ppm reading and divide by 17, this is used to calculate your resins capacity in gallons/per lb of salt) and your iron level. Also, what type of system/size of system are you using?
If I can help further, please let me know!
good luck!!