I'm just posting a second answer rather than try to force this into 500 characters:
I kept your first sentence, although I punctuated it to sound like actual speech. I can certainly hear the intonation you intend, but that requires a pause. So I added an M-dash.
I know what you were getting at with the idea that he's both asking a question and making a statement, but you worded it awkwardly. Saying "It wasn't quite a question" infers that it's mostly a statement, so that also trims some words.
You mention "study" twice in the same para, so I cut the first use.
"Mr. Jansen" is fine until we find later there's a Mrs. Jansen and that both have first names, so I put Robert here, since this is our introduction to him.
A silence only deserves an adjective when there's some kind of emotion in it: tense, contented, aching. "Empty" is redundant and inapplicable. Out.
Now we find that Robert is doing something. This would work better as a response to the other man's not-question, so I moved it up and made it parallel phrasing, which is more elegant and more vivid. It also allows there to be an exchange: speech, beat of silence, movement. This works better than words thrown over a departing shoulder.
I have no idea if a Beretta is properly a pistol or just a gun, but I assumed the one on the desk was his Beretta. I trimmed that to make it clearer.
We leave the study; that's fine. Then we come to the car. I added actual movement rather than have him transport from study to already moving down the street.
IF you're doing a deliberately exaggerated style of writing where part of the humor comes from over-branding, you could keep the Ferrari business. This appears to be pretty straightforward, however, so I would introduce the car description in whatever next scene it is with him, whether he's driving or arriving. My first thought here is that it's just distracting.
My second reaction to the Ferrari is that it's an expensive toy — classic mid-life crisis, compensation for something. So I thought it would be neat to add the idea (not in your original) that he had spent too much on everything at some earlier point, and was now regretting it.
When you mentioned the missing daughter, that tied in really well with the "spend in haste, repent at leisure" idea, so I connected them.
Kept your sanity. ;)
I note that the wife is not at home, but at someone else's house (her lover's?) across the street from her home. Left that.
Since Robert is the only person named, we can simply say "his wife," and then give her name as part of her introduction.
Daughter's disappearance is already moved out of here. Since I established that he over-spent, and the other man and the gun also portend trouble, that shows (rather than tells) the reader that he's taken it hard. So that's out.
"Tacit" is not the word to pair with "exasperation." It's usually used with "acceptance" or "rejection," since it means "unspoken" or "implied." I get that you wanted to say that she was exasperated but trying to hide it, so I reworded that. At this point we're in her POV, so I gave her thoughts and perspective. She has a lover (also showing that she hasn't been the same since the daughter went missing), so she's turning to someone other than her husband for comfort, and she's going to perceive the lover's arms to be warm emotionally as well as physically. That's an important detail.
I also added the idea that she doesn't believe her lover's assurances. She knows something of what's going on with Robert or she wouldn't be exasperated, and it's possible that she hasn't told the lover everything that's going on. So he's just giving her platitudes (maybe to make her come back to bed?) and she's not buying it.
So that's what was going through my head. :)