when you have strings going to parallel you need the voltage be the same on all strings.

Series the 8 together as long as you dont go over the max input voltage. Then maybe use the other 2 on a different system

Did you compute the power loss due to the age of the panels? I think you said some of the panels are 5 to 6 years old. Some of the loss might be comming from there.

your AGM's look fairly new - any reason for not going lithium?

You're voltage it's very low this inverter works at full capacity when voltage it's between 300-360v when conect different panels in series if you have for example 8 panels at 370 w and 1 or two at 200 w all the panels are going to work at 200 w

Open circuit volt is your what you should be using so if you have 6panels at 50 volts = 300 volts then look at your mppt amps use your multimeter test what pv volts you have at inverter I have 6 panel making 250 volts with mppt start volts 140 no trouble to be charging battery early morning at 5watt

What is the max input voltage for your charge controller?

Bro you look 10 years younger