dont forget to change your method to "post". this request deleting all permissions for my folder using path i've get from metadata. You should change command after "/web/xxxxx" to "GetListItemUsingPath" or any other you want. In the brackets put data you gained from metadata.
3. Give access to element. Use ID from author's email from metadata to give to creator of item access.
That All. If I did then you also could do this. Hope helpfull.