Your matroshka doll encryption scheme looks secure, but that depends on how complex your password is and other factors. I use full disk encryption because an encrypted volume can leak info about its contents onto the unencrypted parts of the hard drive. For example, if you browse an encrypted volume with a file manager, it can create a thumbnail of an image and save it in an unencrypted part of the hard drive, or save metadata that a certain icon (such as the Tor icon) goes in a certain folder. Most operating systems also save info on recently opened or executed files, which can provide links to the encrypted volume. The safest solution is full disk encryption.