I apologize for overlooking your post. In case you still need the info:

Your hardness and number of people would indicate a 1 - 1.25 cu ft softener. However, your flow rate requires a 1.5 cu ft softener. So, we have to make a compromise somewhere. A 1.5 cu ft softener can be set to regen every 7 days, but will use more water than a smaller softener. This will amount to around 1000 gallons of extra water use per year. If that is acceptable to you, order a 1.5 cu ft softener. You want to ensure your softener has:

1. 10% cross-linked resin. Because you are on city water, the additional cross-linking will better resist the chlorine in the water.

2. gravel underbed. This is not optional, despite what many softener sellers will tell you.

3. bypass, noryl preferred. These valves get used seldom - the noryl valve is less likely to bind with disuse.

4. Fleck valve sized appropriately for your plumbing. Ensure the valve on the softener is the same size as your plumbing to avoid unnecessary pressure drop.

We can help with setup once you have the softener.