There seems to be a significant amount of confusion here. Sorry if you feel we have not been clear here, and let me see if we can get this cleared up.
There has been no stating that these can be changed x times per year. In fact generally, these can only be changed yourself when changing your main license. However as stated in the ticket a few times and on here, we can do this for you. Not only can we do this for you, but it has already been done for you.
The second part of the confusion is what happens. We do not set the licensed test URL. If you wish for me to do so, I can certainly do that, but we would generally 'reset' the test URL. By this, it means it is wiped. Yours is currently reset, so you can use it on the test URL you specified, on that non-standard URL specified. A URL (test or production) is actually set when the license polls the server. So when your system at that 8443 URL polls the server, it will set the test URL on file.
I am very much confused here as to why you are stating we are not allowing you to change your test instance. Our very first response to you here stated we can certainly do that for you. My first response in your ticket also stated the same (and indeed reset that test URL)
In summary here. You want to set your test URL to a new URL as you are using a different port. Your licensed test URL has therefore been wiped so you can use your test instance on that new URL (the one on 8443) should you wish to do so.