Is there a way to make the Teamspeak server ID custom?
Changing Server IP
If you have your own domain, you can point a subdomain to your Teamspeak.
Have a look at this guide for how to setup an SRV record so that it also points to the port. (So if your server connection detail is: tsfr.uhostpro.com:9999 your domain will account for the :9999 without the user having to type it in)