You are a solar designer. How is it that you are not savvy with electrical stuff? I would suggest taking a CE course on article 220 (load calcs). Very important for folks designing battery backup systems.
The inspector asked for a load calc for the serivce in the upper note, but the lower notes indicate that he is really wanting a load calc for the backup loads. He pointedly asked that the load calc include battery charging, which will be an added load at the serivce (if the system is programmed to allow the battery to be charged from the grid), but not at the backup loads panel. Seems like you will need to provide two load calcs. One for the service that includes battery charging, and another for the backup loads. The load calc for the backup loads panel shouldn't be over 5 kW, and it almost certainly will be if this is for a typical residence. Your options will be to add more Powerwalls or just backup a subset of the home loads as other have suggested. Or maybe you can figure out how to load shed the large loads.
The inspector invoked the amendment to 710.15(A), but I don't think that was necessary since 702.4(B) already says that optional standby systems (like this one) shall be sized to the load when automatic transfer equipment is used.