Hi Josh, thanks a lot for your answer, which is the correct one !
I was just had to tell NPM to point to http://nextcloud-aio-apache:11000 and now the domain verification is working ! Thanks a lot to have take time to help me. 
I remember I had tried this was no luck, but perhaps there was something else wrong at the same time.
APACHE_IP_BINDING is still in 127.0.0.1 which seem to be a good way to not expose it more than necessary.
Regards.