You are missing the port information.
Default is :2710
So something like this should work
$ INSTALLER09 [' xbt_prefix '] = '
http://mywebsite.dyndns.org:2710/ ';
$ INSTALLER09 [' xbt_suffix '] = ' / announce ';
$ INSTALLER09 [' announce_urls '] [ ] = '
http://mywebsite.dyndns.org:2710/announce ';
i dont use XBt myself on this source, so I'm only going off memory, but I think that is about right.
Also, I'm not sure if you can use HTTPS, so i have removed that from your config. SSL works off its own port 443 in the case of web browsing normally.
Although with some server side webserver configuration, I would of thought you can get that to work, but thats beyond the scope of this post.