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Hi @nicvazquez@gmail.com, welcome to the Community! Please read and abide by the Community Guidelines while here, as that will make all of our jobs easier - in this case, specifically the "one question per post" rule is the particularly relevant one here, since multiple questions in a post make it exceptionally difficult to keep track of which questions are still open and which have been resolved.

That being said, first: @dazey77 is correct, you will require a properly connected and programmed shunt-based battery monitor like the BMV-712 or SmartShunt to know the SOC of your batteries; you cannot use voltage as a means of estimating SOC of an LFP bank.

Second, the VE.Bus Smart Dongle for the MultiPlus will allow you to see very basic information about what the Multi is doing via BT, and allow you to: switch the Multi between On, Off, Charger Only, and Inverter Only modes; and it will also allow you to adjust the AC Input Current Limit through BT connection.

All programming of the Multi, however, must be completed via wired connection through an MK3-USB Interface or through the VRM using Remote VE.Config if you have an internet-connected GX device on the system.

Finally, I'm hopeful that you have a Victron BMS on your batteries, as is required, and that you followed Section 3.2 of the user manual and made sure to fully charge each battery individually with a low rate of charge prior to connecting them to your system?