You guys are doing all this the hard way.
The simplest way to make a system that can NEVER feed anything back into the grid is by using a grid powered rectifier and dc link into your system. Its simply impossible for a rectifier to feed anything back the other way.
All you need is to feed the dc output of your rectifier into your solar panel circuit through a diode at a suitable voltage.
At night the solar controller or inverter will think the solar panels are still working, but at an unusually low output voltage.
During the day the solar panel voltage will be much higher than the rectifier voltage, and the diodes in the rectifier will not conduct.
On a really crappy cloudy day, the solar panels will do their best, but any peak loads will pull the voltage down to a point where the rectifier will source whatever extra current is required to support the load.
At sunrise and sunset, the changeover form rectifier to solar and back again will be gradual and seamless.
Unfortunately I cannot post a diagram, but the idea is simple enough. I have be doing this myself now for a couple of years. My smart meter just shows power consumption (from the grid) dropping to zero in the morning and staying at zero until late afternoon. I have no battery, still reliant on grid power at night at this stage, although that will soon change.