Is the VDSL being used for other things? How much actual bandwidth are you wanting to dedicate to NTP? A NTP packet is 48 bytes (but figure closer to 90 bytes total for the ethernet frame to be conservative). From there you can figure how many “queries per second” you want to handle, then through monitoring your NTP server you can adjust the bandwidth settings on the NTP Pool website accordingly.
One Megabit of bandwidth should be able to support about 1,400 queries per second.
To answer your questions:
A - There is always a need for more servers as more devices are coming online worldwide.
B - Yes even the VDSL server would be helpful as long as the IP is static.
C - Yes, on the NTP Pool website you can configure a “bandwidth” setting which controls how often your IP shows up in the DNS rotation. I’ve found that after adjusting up / down on the website the actual usage seems to change pretty quick (well within an hour it will settle into the new level).
The pool doesn’t really need any sort of DNS record for your IP, you can use just the IP on the website as that is what any NTP client will use anyways.
One thing to pay attention to is your router hardware. All the NTP clients making requests can fill up a firewall’s connection tracking table if not configured properly. Since UDP is connectionless it’s easiest just to exclude inbound to 123 from being tracked (if possible). Some residential routers have settings like “UDP Session Control” and “UDP Session Timeout” that might require tweaking.