AC300 as house UPS on Critical Circuits EU model

I have had the AC300 for two weeks. Enough to get to know it a little and discover the capabilities of the Blueitti Service. For example - send a video of error codes. ?.?.? In 7 days I have had 17 error code 800 but that is another topic.

I have read most of the transfer switch issues. I do not want a complete transfer anyway. I want the AC300 to be a UPS on three dedicated house circuits. I want to be able however to switch between the AC300 and House critical circuits if needed due to maintenance, etc. In addition I want the 3KW SMA Sunny Boy inverter on a switched circuit so that it can remain powered in a blackout and charge my AC300. I understand the safety requirements to isolate the grid from my house solar current in a blackout situation.

I discovered that the Neutral must absolutely be separated from the house Neutral. In Germany the house is fed with 4 wires. L1, L2, L3, and PEN (Neutral and Earth combined). The PEN is then split into two busses - PE and N. The PE buss is hard wired to a good earth point.

I have found what appears to be a good rack mounted switch to achieve my goals. The Eaton SB525. It switches both the Hot and Neutral and has a Null position. The earth (ground) and Neutral are tied together from the AC300. At this common point you run one wire as neutral and the other to the earth grounds.

I would connect each circuit separately like this:

Any comments welcome.