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Grid-Tie inverter connection into DB


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I need some advice from you guys about the proper way to install my 2.5kW Solis single phase grid-tie inverter into my DB board. As per the manual, the inverter should be connected in parallel with the mains (before the earth leakage) and preferably through a 2 pole isolator/mains breaker and another MCB limited to 15A.



Attached is a photo of my current DB, but I've drawn it as a diagram as well (it's a small townhouse so it's a tiny DB and all circuits are protected by EL). 



Is my understanding correct: 

- Label existing half of DB "GRID" and label new breakers with "Alternate Supply"

- Add a new mains-rated breaker (63A 2P). 10mm2 Neutral from neutral bar. 10mm2 Live tapped from Earth Leakage input. Label "Alternate Supply"

- Add new 16A MCB. 10mm2 live tapped from new 63A breaker bottom. Label "Inverter"

- Connect inverter using live from bottom of new 16 MCB. Neutral from neutral bar. Earth from earth bar. Surfix with 2.5mm2 conductors. 

- CT Clamp in seperate conduit to DB clamped around live from prepaid meter before mains breaker. 

Here is the diagram of what I mean



A few questions that I have: 

- Only my EL is marked with mandatory direction, the others are all omni-directional. In my DB board, the convention is that the load is connected to the bottom of the MCB. In the case of an inverter, which side is really the load? Should the house mains be connected to the top or bottom of the new MCBs? Does it matter

- Is it really necessary that the new 2-pole breaker be rated at 63A? Since there will only be a single 16A breaker for the inverter connected to it, may it be a lower current rated breaker?

- Is the traditional way to split live to another circuit just to jam another wire into the terminal of a MCB? Seems like it might be difficult to force two 10mm2 wires into that tiny screw terminal. 

- All cables are plastered into the wall without conduit in my house. I'm installing the inverter directly above the DB board. Is there any issue from a  COC-perspective if I chase into wall above the DB and install a conduit. What alternative way is there to get cables into a flush mounted DB?

Hopefully I can get most of the work done myself and get a sparky to come do a COC when all is done and turn it on for me. 



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