since you own CI+ device, the task to revive is almost mission impossible...
Yes, injectso is cute tool and really dangerous if used incorrect syntax
From your story i haven`t understood:
Have you got ANY debug log on the terminal (putty) while connected over ExLink? This is important. But what is bad, that factory reset drops rs232 to uart and then ExLink helps nothing. Just only if ResetButton is present on mainboard, here is a theoretical chance to set rs232 to debug by pressing such a button. If no button, then perhaps it isn`t soldered in and you could shorten contacts and imitate press of such button?
B650-ResetButton-th.jpg
B650-NoResetButton.jpg
I don`t know much about CI+ mainboards and what it look like. Take please good resolution picture of full board (or divide to pieces). Chance is low, but still exists.
What is going on TV when it freezes? Does it reboot? Or still hangs? If hangs, it is good, means, we have time to play with ExLink
More info please!