Storm over Warlock was SciFi, and there were at least 2 more related books I believe, but I recall no man stranded there. In either the second or third one there was a woman who escaped from some capture on Warlock I believe.
But Norton's series about The Witch World may be more likely your memory. One earth man goes through a gate of time and space to escape from people hunting him and ends up there. Women called witches have powers. He helps their group fight off enemies that are more science than magical.
He marries one of them, and against all custom she doesn't lose her power afterwards. They have triplets, unheard of in that world. Two sons and a daughter who grow to become a warrior, a warlock, and a witch or sorceress (the two are somehow slightly different in the powers they call on, and some can use both).
Those three travel, and get caught up in an ancient Battle of Dark and Light.
There are at three different cycles or series about the Witch World.
Escarp cycle, High Halleck cycle, The Turning.
Coincidently, I'm just reading the Escarp cycle now. I've read most of her books before, but there are a few here and there in different series I never read. I'm trying to reread the series and catch the ones I missed before. Unfortunately for people trying to do it without buying them, it's probable that few libraries will have all of them, particularly the older ones. In fact, some are out of print and may be difficult to find at all. The Science Fiction Book Club has reprinted some of her's a couple of years ago, but still many are rare finds.
A list of the books of The Witch World .
Norton wrote many others, here is an official website , but there are many fan sites as well.
We have at least a couple of dozen of her books ourselves, and have bought some books by newer writers that continue one series or the other of hers with her, and later her estate's, permission. Indeed, a couple of the sequels were published as collaborations, then continued after her death by the collaborator.