Teknic Clearpath SDSK with HLFB + MESA 7i76e

Let's take these questions one at a time, starting with the simplest.

To e-stop when the drivers report an error, take the driver error output to a GPIO pin, and then in HAL link that to the corresponding amp-fault-in pin:

linuxcnc.org/docs/2.7/html/man/man9/motion.9.html