As for the role of GHG's they can affect the recovery and this leads to a climatic feedback according to our current knowledge. That all parties fully abide by the Montreal Protocol 2. That the composition of the atmosphere remains as it is today. However, the European Commission has questioned the validity of the 2nd assumption. Also, as I have previously mentioned the mass transfer between the troposphere and the stratosphere can be a significant sink for certain GHG's.
Monitoring is essential to test models.
But we need predictions to aid regulatory decisions. We are not there yet with GHG's. Regarding CFC's the surface measurements do superficially show a negative trend. However stratospheric processing of these gases is very slow and the complete cycle from the time an air mass enters the stratsophere in the tropics until the time it reaches the poles is of the order of 2-3 years. PSCs are essential for polar ozone depletion, but not for the upper stratosphere low latitude losses that have been also observed.