Growatt - SPF 3000TL HVM-24V - Questions

Good morning all you smart people

I have the inverter in the title. Works like a bomb, love it. I do have a couple of questions.  I use (SolarAssistant connected to USB to monitor my vitals)

I have 2 x 120ah LifePO4 batteries https://sjandrews.co.za/shop/s-j-andrews-2/lithium-batteries-s-j-andrews-2/lifepo4-lithiums120-12-8v-12kwh-s-j-andrews/

They have built in BMS but no comms.

Question 1) My load being reported by the inverter seems to be uncalibrated. I have a server running 24/7 on the load (+-55Watt) that is not reported by SolarAssistant. Solar assistant has a pseudo BMS where is can calc your SOC, but because this load isn't reported, it's inaccurate. 
Is there a way I can calibrate my load reading?  I've found the "secret menu" on the growatt. in there you can change the voltage of the load, input and battery. I've measured with a multimeter and made a 0.1v adjustment, but it had no effect on the load being reported. Should I make a bigger adjustment? 

Question 2)

If I decide to go rack mount Lithium with Comms port, how do I know the comms will work with the inverter?  According to the manual only one battery is supported and that is not available in SA.  Surely something popular like a pylontech or Giter should work?

Thanks