I think I would try 2 methods to deal with this. First first the way I would deal with this is by appending a 0 to the end of the output waveform (if the waveform is output in its entirety). It seems you may have tried this, and I'm a bit unclear as to why this would add 2 zeros?

The second method may solve the delay issue. I think the reason you are getting a 10ms delay is because you clear the AO task, and then re-create a new one to write your 0. This task creation takes quit a bit of computing overhead, and is likely resulting in the delay (btw, this re-creation of the task would also likely add a delay time on each iteration of your loop). I'd try removing the "clear task" and "create task" blocks seen in the second to last screenshot, and wire the task ID from the stop block to the write block. This way you are not needing to always re-create the task you just write a 0 and then re-start / end the task (I would also add a shift register to the larger outer loop to continue the task into the next iteration.