For that use case you don't really require CTs I suppose. I imagined myself being in such a situation, and what I'd do is the following.
(I assume that your inverter output power is enough to power all your needs. If it's not the case, then I should rethink the whole setup)
In case of frequent...
If that's still acutal, I'd be happy to help.
Can you please clarify what exactly you mean by 'supplement the grid from battery as needed'. It's quite confusing to me.
Also it's not clear to me if you have additional grid-tied solar system or you referring to your hybrid deye solar inverter...
I'm wondering what is UPS output exactly? And is there any load connected to it?
Also, you mentioned 'the inverter switch'.. what's that?
250-300W doesn't seem to be a self consumption of the 6kW inverter itself