he informed us that he didn't agree with the survey stake and we would be responsible for 1/2 the survey cost to resurvey it.


Just BS. If he disagrees with a valid survey, and is not a licensed surveyor, he does not have an opinion.

He then later came back about 45min later and started to threaten us with his status of being a police officer
Grounds for disciplinary action in some jurisdictions for intimidation. Get witnesses and record any further conversations with this individual.

What kind of action can he really take if both of our surveys agree? Pertaining to making us move our fence over 15ft from our property line.
Is the 15 foot lane a deeded easement? Or was it just granted by verbal permission at some point?