I like it as a story, but I think you might have gone overboard with the captions and the attention to detail. The more details you want in a single panel, the more will be obscured if you have multiple captions and speech balloons. It's a fine line to walk, you always have to ask yourself if a detail is important, or if it's fluff.
I noticed you're describing the story as if in motion... for a script this might actually hinder the artist.
We now see the rest of the room, John's area. There is a third desk and a third computer, both of them facing the wall. Near the desk and next to the wall is another stool. On it lies a magazine, closed. (See sketch.) Behind the desk is the room's only window. John is making himself comfortable in his chair. He has taken his jacket off in the meantime. It's on the hanger, though we can't see it. Casual clothing under it. We are looking from a place behind Sharron's head, only a part of which is visible. Her shoulder also may or may not be visible from here.
He has taken his jacket off - important to note, it's a visual cue.
in the meantime - this is implied so there is no need to mention it.
It's on the hanger - this would be important were not for:
though we can't see it - which makes the whole jacket thing redundant to mention.
There is crazy mad attention to detail in this one panel:
You see part of someone's head.
You see the main character sitting in a chair.
He's not just sitting, he's making himself comfortable.
He's wearing something casual.
There is a third desk.
The desk has a computer on it.
Both are facing the wall.
This wall has the only window in the room.
There is also an extra stool.
On this stool there is a magazine.
The magazine is closed.
I count 11 visual elements that you want your artist to put on paper, eleven details that are important to note.
To my eyes it reads like a story you've converted to a script for a comic. It's solid as a story, but as a script it reads a but uneasy because of the many details and descriptions you are giving your artist. This might be me, because I'm a visual thinker, and maybe because of that I can see a whole lot of movement and flow in a script that deals mostly with the illusion of movement. The pictures don't move, action is implied between panels.
This would read like a solid story, it will end up being an enjoyable comic if your artist is capable of delivering, but the format of a script is something that I find myself struggling to give feedback on. So what I just mentioned above, it's just me speculating and pointing things out that raise questions in me. Which boils down to one single question "how much detail do you think is appropriate and needed for a single panel?"
That's the only thing I've learned fromm comic-book scripts, you start with the bare minimum:
A room, Jason is in the middle of the room, he is smiling,
Jason is in the room and Susan is also in the room, she is frowning.
Jason: "What is wrong Susan?"
Susan is still frowning, Jason has a neutral face.
"My neighbour ate my baby brother"
And to be fair, even the room is more than the bare minimum, since the three-panel story could just as easily be told with just the two characters' faces.
So yeah, basic question you should ask: what's an important detail for the reader to see and take notice of?