WordPress hosted on QNAP: address problems

Hello,
I am a newbie in this world and need some help to get things working…

I setup WordPress 4.6.1 on my QNAP using it’s local IP address. I created a Blog and start using locally (on my LAN) to make test and all went ok.
Then I registered a domain and wanted to “publish” my blog.
I tried to:
– Changed in the WordPress general tab the URL from <my_local_ip>/WordPress to http://www.mydomain.com
– Using UPDATE queries on my SQL DB to modify all the entries (not only the 2 URL in the wp_options table, but also all the posts)
– Using plugin better search and replace

I always have the same problem: I can see some data (like the frontpage, but without proper layout and so on..) using http://www.mydomain.com, but the page links are not working at all. Also I am unable to go to the dashboard. I have to manually update the URL in wp_options table to go back to the local version…

Any ideas?
Thanks