I would personally advise to use H264 and definitely not the so smart "+" codec on.
Also crank the bitrate up as much as possible via constant not variable.
You should be able to have one IVS rule for a tripwire and another rule for intrusions. So rule 1 is a tripwire and rule 2/3 intrusion, or similar configuration. Then subscribe to your required push notification.
Crazy that you have to complain about a service or product because of no assistance from a manufacturer/seller. Then post on a separate internet site for assistance for warranty.
Hopefully all works out for you.
Can I ask when the remote access was not available please.
Another thread from a trustworthy forum contributer has suggested the P2P servers/services has a possible issue.
I'm guessing a bit!
I suspect your network settings on the new router and configurations do not match the DVR. Is the P2P still active and online via network settings on the DVR?
Have you checked that P2P is still active and "online" via network settings on NVR. Also in network settings check DNS preferred 8.8.8.8 and alternative 8.8.4.4?
My initial thoughts would be that your Home Assistant software is causing the problems described. Other software will most likely never integrate correctly.
Have you isolated the Dahua camera away from the Home Assistant demands, to see if the problems resolve?