OLD Latche conversion to a CNC

I'm not sure I understand the issue.

There is no logic in the hal file to limit the spindle acceleration

No following error would be expected since the spindle is not an axis

I want the machine to stop if the spindle stops or the RPM slow down.
Also, when starting the spindle, there should be a set acceleration.

It looks like you have the needed components for this (limit2 and near)
but they are not connected.

That is you have the PID spindle speed  command coming directly
from the commanded spindle speed:net spindle-vel-cmd-rpm => pid.s.commandRather than having been fed through the limit2 component.

 Also the limit2 maxv (which limits the ramp rate) is not set

Similarly you do not have the near component connected
nor is the near components  scale or difference values set