No one is a "Rev" based on ordination. A person is a "Rev" based on someone calling him by that title.
In my experience a man is called "Reverend" when he is an ordained minister but no longer a Pastor, a Professor, and without a terminal degree.
I, being retired, am no longer a pastor or professor and thus no longer entitled to be called by that nomenclature.
I have a terminal degree so many people call me "Dr. Cassidy" (which I eschew, preferring to be called "Tom" - which then morphed into "Dr. Tom" - sigh, what are we going to do!).
But without the terminal degree, what term would recognize my status as an ordained minister of God and still maintain the distinction that would not be apparent with calling me "brother?"
I think all of this is a matter of personal preference. I don't like being called "Reverend" but certainly would not castigate a person for using that term in reference to me.
In necessariis unitas, in non-necessariis libertas, in omnibus caritas. (In essentials unity, in non-essentials liberty, in all things charity.) (Usually, but probably incorrectly, attributed to Augustine.)