Fleck 5600 softener(5E45-2 media tank) salt regen settings?

Hello all- Im hoping someone can point me in the right direction with my Fleck 5600 ecominder water softener. Its a basic model, 1.5cubic foot tank 54" tall,10" diameter( I believe it's a 48000 grain tank), with a 12 day timer, which has pins to set the regen frequency. I live alone, and use very little water. I feel its regenerating too often, as when it was installed in 2011, it was pre-set to 18lbs per regen, every 6 days at 2am. I recently lowered the salt per regen to 8lbs from the 18lb factory setting. The installers said they don't usually mess with the default setting, and left, so now I'm wondering WTF? lol. My water specs at the time of install are as follows: PH 7.1, Total Hardness 51.4 mg/l, nitrate nitrogen 10. mg/l, arsenic <.5 ug/l, calcium 17 mg/l, copper .022 mg/l, Iron .31 mg/l, lead ,72 ug/l, magnesium 2.2 mg/l, manganese .0023 mg/l, sodium 40. mg/l, turbidity 3.9 NTU, and uranium <.5 ug/l. I know this is a lot of info on water, but I want You people who understand to have the proper info. I hardly am ever home. I shower every am, all water appliances are low flow. Do maybe 5 loads laundry a month, with an HE washer, run dishwasher 2x a month, etc. I don't think I even use close to the 70 gallons a day avg that I read online, but if I do somehow, could someone point me to figure out how many "Grains" of hardness my test equals out to, and recommend a regen\salt lb setting to start with? Right now, I'm set to regen every 12 days, with 8lbs solar pellets. I just set this a few days ago, so I could always change it back if needed, but even if I go on vaca, and run NO water it was pumping 18 gallons per regen, which seems crazy. It drains regen under my deck, but the excessive salt is actually starting to kill my lawn 12' away. I have a dug well, and live in the country. No town water fyi. Any info is appreciated! Mike