The DUC updates your-ddns.hostname.org with your actual public IP, your storagenode should use your-ddns.hostname.org:28967 as your contact.external-address:. In such case all should work as expected while the DUC is running.
If you can find a DDNS section in your router, you can try to register there your-ddns.hostname.org with your No-IP login (email address) and password. If you would be succeed - then you can remove the DUC from your PC.
However, the contact.external-address: of the "C:\Program Files\Storj\Storage Node\config.yaml" should contain your-ddns.hostname.org:28967 in both cases.