I'm looking for different ways to describe this man's reaction as if he were a character in my story and he reacted to something bad. I know I can say "the smile vanished from his face" but I'm looking for other ways that would more accurately describe the change in his facial expression. Edit: if the above link doesn't work, the video can be seen here: https://www.directupload.net/file/d/6515/6pg9rr8o_mp4.htm
How about, "His smile faded and the light left his eyes at the shocking revelation she had just made." Or, "His eyes went flat and his grin vanished at her comment." Or, "Shocked, his eyes got that distant look everyone knows as the happiness fled from his face." Plenty of ways to describe it.
To ease the tension, he joked, "you have my permission to sleep with other men." A toothy grin creased his face. "Maybe I already am," Laura responded. The smile on his face wilted away. In stunned silence, he stared at her. I understand "wilt away" is used for plants. How literary is it to use it for a smile?
To me it's pretty staid. It's mildly creative but not jarring. It's been used before. Not as common as "eyes flashed," which also doesn't literally happen, but it's safe. On a scale of 1 to 10, with 1 being Jonathan Swift and 10 being Cormac McCarthy drunk on Absinthe, I would rate this a 4. It's definitely imagery, yet it's not cereal mascot bonkers. I don't think most people would even notice it. It's not like saying "his smile disintegrated" or "his smile perished" which would be too active, but it's softly there. You would accommodate it with some simple lines around it, which you have.
It dribbled away. It oozed away. It morphed into blankness. It teleported into oblivion. Scotty beamed it up. It disintegrated, shattered, sagged, melted, evaporated, vaporized. If I get nightmares, I'm calling you at 2 a.m.
The thing about beats and metaphors is that you want them to make sense, but not be too cliche/overused. So saying "he frowned" is fine if it's not overdone and the sentence doesn't need additional description based on the scene. "His smile wilted" fits the bill well, it's understandable in context, and it's not super common. One book I read (it was in regards to metaphors and cliches) said to google it (in quotes for exact matches) and if it has millions of hits you may want to reconsider it. If you google "smile wilted" you get about 30k hits, so as has been mentioned, it's been used. But if you google "smile vanished" you get about 700k so it would appear to be the more common one so not only would you want to consider something other than "smile vanished" since the smile doesn't go way immediately in your scene, but also because it's a more common phrasing. But using google is not a very scientific approach, and that doesn't mean common phrasings are necessarily bad. I'd probably go overboard with it in this scene with something some would consider cringy like: Despite the constant neglect, he was startled by her change in behavior, yet found her displays of independence amusing. "So what are you going to do, leave me for someone else?" "I already have." With just three words his smile wilted away, as if the Goddess Persephone was departing his world, taking the joy and life giving essence she once provided.
What's wrong with faded evaporated withered away wilted or perhaps crumpled These are fairly inconspicuous. I'm assuming you don't want to draw attention to the description itself. Google Ngrams shows that "wilted away" is all but non-existent. It sounds like a confusion of "wilted" with "withered away." The words make sense in themselves, but as an expression it sounds like an unwitting mistake.
I think the comma may need to be a semicolon. The construction is similar to more common sentences like "His face fell, the light dancing in his eyes." where it's implied "light dancing" happens concurrently to the main clause, so I'd avoid it altogether, but that's more a matter of taste.
In the previous vein: "His face fell, the light that had been dancing in his eyes dimmed, as did his smile." Another alternative: "His face fell, the light that had been dancing in his eyes dimming, as did his smile." A little more 'active'
This is a perfect situation for clever analogy. His face looked a little like a basketball after a leak let half the air out.