The important thing to notice is that the prefix part, the 2607:f2c0:a000:54: does not change. It is only the lower 64 bits that chage.
This is important because it the high 64 bits come from your ISP and the low 64 bits are set locally. If the high 64 bits do not change, you have a static range from your povider and you do NOT need a dynamic DNS service.
The oofd thing is, is that you do not seem to have a SLAAC address, the address thatis derived from your MAC. One of your IPv6 addresses that are shown with ipconfig is a PE address, an address that changes every 24 hours and that is used for outgoing connections. Because it changes every 24 hours, it can not be used for incoming connections. The SLAAC adderss stays the same, but unfortunateley I do not see one. Maybe SLAAC is diabled on that machine?
I suggest you configue a static IPv6 address for the BBS machine and advertise that for incoming conections. I would have to look up how to do that. Perhaps Tony can guide you through the netsh encantations to do it. He obviouslyhas done it before.
