Your Arsenic level is over double the EPA MCL.
Thanks for getting a proper test done, this makes designing a system a lot easier.
The MCL for Arsenic is 10 PPB, you are at 22 PPB. The water should not be used for drinking purposes until this is taken care of.
A standard softener should do you just fine for the hardness and small amount of iron. How many people are going to be living here? We need to know that to size the capacity. Be sure irrigation is seperated from the house water.