Once he realises you have dropped the rope and are giong to let him DROWN he will be TERRIFIED... THAT is when he will look at the OW and reconsider...
Right now he thinks you are sitting at the phone waiting for him to call you... why would he leave the OW when he thinks you are waiting for his call?
No contact takes time... its not going to happen overnight... eventually he will start to realize he can't get a hold of you and he WILL PANIC...
Its more or less the same feeling YOU HAVE... You dont' like it much... trust me, he aint gonna like it much either when it hits him... Just stay strong and don't pick up the phone or reply to texts... He's testing to make sure you are there to sve him if he needs it... if you reply it will set you back
Better yet give your friend your phone so you can't reply