I think you could easily cut several pages from this to get it under your limit by just condensing your descriptions and actions. There's a lot of redundant words used.
Take this scene: -
INT. ROSE'S BEDROOM - CONTINUOUS
Meanwhile Thomas runs to her bedroom and tries to grab all the pills from the floor and the box. As he hears his mother coming back he quickly hides some leftover pills under the rug and runs out of the bedroom to the kitchen throwing everything in the trash.
Rose in shock discovers that the pills and the box has gone.Visibly confused and lost she searches her bedroom. She looksaround and under the bed. Not finding anything she sits onher bed. Her head in her hands shaking it from left to right. She stops herself from crying and sighs deeply. With a shaky
hand she grabs the glass of water nearly spilling it and drinks. Thomas comes back from the kitchen exhausted and falls to the ground, leaning on the wall in the door opening between the bedroom and the corridor. Relieved, he is breathing heavily from the rush. Tears forming in his eyes.
The first problem, is you have said the scene is in the bedroom, but then you have Thomas running TO the bedroom, so that isn't correct as you're describing something that's not taking place there. Then at the end of that passage, you say he is in the kitchen, again this would have to be a new slugline (but, is it even necessary to know that he puts the pills in the bin here?). You do this a few times in the script (at the end you say it's in Sam's shop then describe them in the street) so you need to look at that. Anyway, back to the actual text, I'm no expert writer like some guys here, but I think you could write the exact same scene above in about half the lines:-
Thomas bursts in and frantically gathers up the pills. Off-screen, FOOTSTEPS approach. Thomas kicks some stray pills under the rug and scarpers.
Rose enters, surveying the bare floor, confused. She searches on her hands and knees, nothing. Rose sits on the bed, head in hands, sobbing with grief. She composes herself and takes a sip of water, hand trembling.
Thomas re-enters and slumps against the doorframe, out of breath. His eyes well up.
I think you could also cut a fair bit of dialogue. It's a little on the nose and repeats the same points at times. Try to make it sound like a more natural conversation, you don't need to explain every detail. If there are things that the two parties talking both already know, and you want US to also know, be a bit more subtle with the exposition. So, for example, instead of the ex-husband saying "do you think being gay was easy?", perhaps have Rose make a snarky comment like "Surprised you didn't bring your boyfriend with you to really rub my nose in it!". We will understand that he is now gay AND how Rose feels about him, meaning some of the other dialogue where she puts across her feelings can perhaps be cut.
For me, I wasn't too sure about the ending. I think you could have perhaps finished the story on scene 15. But overall, it's a decent short drama and with some re-writing I think you could get it to work. Good luck with it!