Sounds like your DME might be bad, or your new EWS wasn't programmed correctly.
You say that there has been times when the car didn't crank. Then I heard you say that after your mechanic worked on the car, he found a way to start the car again.
Sound like your DME could be loosing the synchronization with the EWS, or vice verse.
Ask your mechanic if he has tried to do an EWS to DME Alignment to get the car to start.
If this is true, have the mechanic reprogram the EWS and test the car for a few days. (I have instructions on how to to this.)
Otherwise you will need to replace your DME, which is not a big deal.