I don't know what I can say.
Yes, I have used the phrase, "and hence." I don't write that phase every day, but it's part of my lexicon.
FWIW, many years ago, I wrote an 850 page+ Ph.D. thesis (engineering) which was read, prior to defense, by a UCAL Berkeley Professor of English who commented that she really disliked my writing style.
It's just statistics. ;)
Most people do not use "hence" every day. When they do, most people do not add "and" to hence.
It is an remarkable coincidence that the author of the ransom note used the incorrect phrase "and hence" as did the Ramseys, one year later, in a note to their church.
Then you're saying "and and therefore". "Hence" = "and therefore."