IMO, there are two types of metalled footway across the verge and they are clearly distinguished from each other. The VAC are distributed only where there are off-street residential parking areas. The remainder, which are barely more than shoulder width, are set in pairs either side of the carriageway.
OP, IMO you are entitled to park adjacent to your dropped footway because its purpose is to provide vehicle access to your property, which does not have a shared drive, therefore as the occupier you are entitled to claim the exemption.
But IMO you should still tell the authority in writing.
As regards the current PCN and contravention, all you've got so far is mitigation IMO.