I remembered something else that can be really helpful, which is just to make vaping as easy as possible:
When he goes to work, have together everything he needs: freshly filled and tested cartos/carts, juice, chargers, backups, the pv fully charged, and a kit/case neatly and simply set up with everything he should need. This might help ensure he does not get irritated/frustrated and just go grab a pack of smokes.
On the communication side of things, as we were sitting together one day, I simply shared with him why I am hoping that the pv works out for him: I love him dearly; he is my best friend, my heart; that if at all possible, when we are eighty, I would like to be holding his hand, not flowers at his grave site. I think he understood.