happy to see your recovery is successful. and that you have managed to drop to 0 nic.
no one can possibly answer your initial questions as to potential effects of vaping on your cancer - or if modifying it by avoiding certain mods etc would help.
from a person with a bit of a health background - theoretically anything that causes agitation/damage to cancer (or even 'normal') cells has the potential to cause an increase in mutation/cancerous cells. nicotine is definitely something that might be able to do this. that being said theres no research - and my thoughts are just theories based on a small amount of pathology I learned in school. This is probably why your specialists wouldn't comment on it - any comments on their part would simply be an educated opinion - not anything that should be given as medical advice.
my own humble opinion would be to take a similar track to what you have been doing.
again - very glad your treatments have been successful - and that you yourself have been part of that success in taking ownership of your diagnosis and your health.