Laser engrave using Linuxcnc

Hello everyone, right now I would like to change the function of my 3d printer core xy to become a laser engraver machine. I have attached the pictures of my BoB and Laser ttl module below.
And honestly I have no idea how to make this works. I have tried to connect the ttl to the pin 16 in my BoB and the power to an external 12 DC power source. I used the 12 DC PS to power my BoB too. But what I found is my laser keep turns on and I couldn't turn it off through the spindle button on the linuxcnc gui.

And then I found out that I have to use the M68 or M67 to control the laser. Then I tried to put M67 E3 Q1 in my g code files, but it gave a message "Invalid analog index with M68".

Can anyone here please help me to get this things work? Do I have to modify anything in the .hal files?

For the pin 16 which I set as the pwm, it's written as "net spindle-pwm => parport.0.pin-16-out" in the .hal file.

Here I attach the g-code which already has the M68 written and the .hal file, also the error I encountered when I open the g-code file.

on line 11, you have this which is invalid
if the intent is to turn it off it probably should be

Does it mean that I have to change the line 11 with M67 E3 Q0?

you may read the syntax of the g-code quick reference
www.linuxcnc.org/docs/html/gcode.html