Hi lancelot,
Your charge controller is slightly undersized. The datasheet for the MPPT 60 150 states the max output power is 3500W, but this is at 60V. The limiting factor is the current output of 60A which means 2880W at 48V.
The XW+ will always draw some current from the grid if sell is disabled. Also the load shaving function will only draw down the battery voltage to the value of Grid Supp Volts setting.and will switch off completely at V= Recharge +0.5V. Have you tried enabling Enhanced Grid Support mode instead of load shave?