Well then the by-law seems to give you an exclusive use right to the common property, provided the area is used for parking. It currently isn’t being used for parking and can’t be used for parking, so on the face of the by-law you don’t have a right of exclusive use.
What is unclear is how the area came to be converted to a courtyard, and what was agreed by the lot owners at that time. You say that it was converted and the gate installed by the Lot 2 owner and the previous owner of your lot – what was agreed by the two of them when that occurred? Are there any records? What was represented to you by the owner of the property when you bought it?