Thank you for the review
You're welcome.
I don't know how to say around what her hands are cuffed, in any language

What I meant is one of the 4 pieces of wood (legs?) which the cupboard stands on.
Visually, I can't picture this. There is a 'pole' separating her joined hands from her back. Given the short link on most handcuffs, I can't see her managing to twist about enough to reach into her back pocket. This is a situation that sounds good on paper but I don't think would work in reality. Seated, she would be low to the ground so she should be easily able to pick the keys back up if they fell. Also this has to be a massive cupboard or she's going to pull it down on herself. If you have a pair of kid's handcuffs and a cupboard, try it. Just don't rattle the cupboard. We don't need to lose a screenwriter doing research. [NB: kid's handcuffs don't require a key to release them.

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I think it might work better to have Barukh take the keys from her. After she's handcuffed to the foot of the cupboard, slap it on the tabletop in front of her. After they leave, she manages to bump them to the floor and try to slide the towards her. At the last moment it gets bumped out of reach.
About Barukh, yeah, a good point, although the brothers haven't met for 9 years.
Still, families talk. It's hard to imagine no one would mention her, a nephew or a divorce. Especially if it was a kidnapping. It's possible, it just felt a little difficult to believe given the twists and turns.
What do you mean by rough edges?
The characters still don't act naturally. They feel rather forced in their actions. Why would a Ilana throw away the picture of her and her son? Why would a "sexy 35 y.o." fall for a "40 y.o. with a belly" whom she fully believes is a criminal? Does it make sense to drive back in a van knowing it has a bomb that could go off? Barukh is going to hold his own son at gunpoint? Ilana's scene with Sami and Shahar at the school feels off given their relationships. Barukh is at home and doesn't notice that Ilana is gone (she ends up at the school)? These inconsistencies just make the story feel unbelievable. Little things that build one upon another.
Perhaps you should introduce a different cop at the school. Maybe the first one who stopped him to re-use an actor. While he handcuffs Sami, Shahar knocks him out. Have Shahar take Sami and the two suitcases to the van. By making Shahar shift from passive to a more assertive role, he becomes a more interesting character. If you want to keep Ilana in that dominant role, you need to work out better how she interacts with her lover/boyfriend Sami. Since this is a short, I'd take the easier way and stick with Shahar. It's perhaps sexist and expected but expedient.
Have Shahar confront his brother and learn about Avi at that point. Then the freed Ilana appears packing and ready. Barukh grabs Avi who bites him after getting Ilana to lower her gun. Then when Avi makes his escape, Barukh goes to shoot Ilana when Shahar acts heroic and takes the bullet. Barukh slips out the door. The cop arrives and finds Ilana tending to Shahar. She directs the cop after the van. You can do a cut away to the detonation scene.
Personally, I'd put Sami in the coffin with the tape gag. What draws Barukh attention while racing off is the tapping in the coffin. When he reaches back to open it, he finds a panicked Sami and sees the bomb. Maybe a note, "Kill the courier" taped inside as a nice final touch. Before the cop leaves the house, we hear the explosion.
The story is good but has rough points that stretch believability. I think with a little work you can polish it up.