Hi, I have the same problem with my NVR4216-4KS2/L recorder on DMSS.
I have one question to what you wrote in the first post:
"I also bought a public static IP address from my provider (they removed me from CG-NAT), I forwarded ports 37777 and 80 on the ZTE F680 router and set in DMSS to connect via the IP/Domain option, but neither that didn't help and the live stream and viewing of the recorded material are still choppy and constantly twitching..."
So, if You have public static IP address and have configured DMSS to connect via the IP/Domain option - it means that DMSS connects directly to Your NVR, without P2P service. So it works similar to using a VPN and P2P is not a bottleneck? Do I understand it correctly?