I've decided to go with a PCB mount transformer for the isolation since its rugged and I know it works from OZ's experience.
I havent done much with the board because I was waiting to get a ADS1115 ADC module in the mail. I want to use this for current measuring because it is so much more accurate than the Arduino nano. It can also measure current in both directions which will really come in handy. There will be spare ports for other shunts such as charge current.
All the experimenting has been on a NodeMcu which is a WIFI enabled device. I've been sending data to the cloud so I can read it remotely which is very cool.
My inverter creates terrible noise that drifts by around an amp on the arduino. I tried some rough software filtering at first but it didn't do much. After some reading I learned about some simple hardware filters. I just put a 10K resistor in series with the ADC port and added a 10 uf cap between ADC and GND. Noise is down to around 100ma. I'm sure if software filtering is added this can be brought down substantially. I'll probably go with this for current measurement in the final design. internet connectivity might have to wait till the next revision