I looked at the formation of your Embedded RP, and it looks correct.
Your RP = FC00:2:2:2::2/64
Your Embedded RP Address: FF78:240:FC00:2:2:2:0:1. This address is correctly formatted assuming you want to use the first multicast group (then trailing 0:1) possible on that RP, and the scope of the multicast group is global (8).
Also, your show commands have the correct output (like on the RP, for example) where it shows the correct (*,G) entry.
The problem is your lab is extremely complicated, and frankly, I don’t want to spend two hours troubleshooting it. I suggest you start by creating a simple a network as possible (just three routers) and validate your Embedded RP setup works there. I am probably not telling you anything new in that often problems with multicast networks are RPF failures.
Some of your other questions:
FF7X:0 The 0 listed here will always be a zero. That’s just how the address format works.
As far as /64 = 40, I answered this in my earlier response. 40 represents the prefix length in hex. So if you wanted a /128, use 80.
I don’t understand what you are asking in your paragraph about the static ipv6 default route.
ipv6 pim non-dr-join – I had never heard of this command, but I did some research on it. It appears as though this is used when PIM enabled routers are part of a FHRP (first hop redundancy protocol) environment, like VRRP or HSRP. When you enable the non-dr-join command, the router that was NOT elected as the PIM DR still registers itself, but using a “Block” flag. This is block registration allows a quicker transition to the “forward” state than if the non-DR didn’t register at all in the event that the DR router fails.