The issue was with the 1*78 extended home control events.

The commands I was sending to the security panel were in the limited format, not extended. Changing the 1 to a 0 got me working. It's a really simple interface, not real keypad emulation, only one partition, and a handful of zones. No need for the extended commands.

Thanks for confirming the rest for me though, first one of these I've ever done.