Can these two problems be solved using the Automation Blocks AE Extension?

1. Loop over the comps using the For Each Project Item block, then set the Downsample Factor using the Set Attribute of Comp block

2. Loop over the layers of the active comp (or of The Only Selected Project Item, if you want to process the layers of the only comp that is selected in the Project Panel but may not be active) and then Set the Attribute "Locked" of the Layers to false .