Last night I have solved the repo init problem!
I put my solution here if it helps anybody.
I have found a hadk-faq useful hints website where it advised: if the 'repo init' fails because of gpg, use the Well, unfortunately it didn't help either but then I realized that if I was outside of the PlatformSDK/ubuntu chroot, I was able to run the repo init.

Then, before the 'repo sync --fetch-submodules' command within the .repo folder I manually needed to create the manifest.xml symlink to point to the proper file, but after this, finally, the android source has safely downloaded.

At the end I ran out of space on my /. (My /home was part of the / partition and the downloaded sailfish + android source eat up lot more space than I expected.) So needed to resize another partition, create a new one and mount that as my /home. Plus needed to copy everything from my old /home into the new one.
Now it is ready for the next step 'Configure Mountpoint Information'
I know it is still a long way to go but now at least have got all sources I need.

Edit: I forgot to mention that I needed to install the gpg2 on the host (sudo apt-get install gnupg2) because that was needed for the 'git config --global gpg.program gpg2' command.