What happened to the property caresses real face

He strokes strands from my face .... "friendly" gesture?

I believe the two of you seem to be missing something in your relationships.
Otherwise the fact that you are both taken would not be a 'hook to the story' but something incredibly beautiful, namely that you can deal with a colleague of the opposite sex in an informal and friendly manner, even though you are in a relationship.

The fact that he has to remind himself of how great his relationship is by telling you things somehow also points in this direction for me.

As for the actual plot:

'You have your hair in your mouth' would have been enough, right? And then touching your lips at the same time, goes a step too far for me beyond 'friendly / collegial'.

Your choice of words is conspicuous with you, his gestures with him.

I like it