The way I see it you will need to zero the stop every time you turn on the machine since it will not know where it is. If the machine is on all day it's not a big problem since it has to be zeroed only once a day.
You will need a positive lock on the stop or it will move every time you bump against it. While the motors are powerful and should resist moving while under power it still may move a fraction.

 

The belt can not be locked in any meaningful way. One way to solve the locking is to use a thin threaded rod, like #6x32. It has teeth every 1/32". Run it the whole length of the side. Have a small #6 rod, maybe 1", engage into the long run when you have reached the stop position. It will have to be done with a servo or with an electromagnet and spring. You'll have to write the code for it to engage and disengage when needed.

 

What is the status of this project?

 

You continue your project "Mit Saw Stop Block"

I also want to get closer to doing something like "Table Saw Fence Control"

I find programming difficult

 

thanks. Maybe the discussion will resume there as well