Dyn's answer is correct. The DynDNS Pro / Remote Access service was designed for personal or SMB use, never to provide services to third parties. Your concerns regarding the functionality of the Dyn Updater confirms this as well. Dyn used to offer an appropriate service called Managed DNS, but this is now Oracle's OCI which doesn't do the same thing, because it does not support the usual kind of Dynamic DNS.
You can make your environments a bit more secure by not using the Dyn Updater software (again, this is for personal use), but another update client like the built-in client in routers, DVRs, NASs, IP cameras, etc. Or another software like Marc's Updater. Also, you better use the Client Updater Key instead of your account's password for the update clients.
If you are looking for an alternative provider of such services where you can configure update credentials per hostname, you would have to register an own domain and to use a DNS hosting service like https://freedns.afraid.org/ for your domain. This and other services have even a free option.