Sbrocchi is a colloquial and expressive verb that means 'you freak out' or 'you lose it'. It's a less common, more informal word than typical verbs, making it interesting and memorable.
In the song, the lyric "Sbrocchi ma sei romantica" (You freak out but you are romantic) highlights a charming contradiction in the person being described. It suggests that despite moments of losing composure, her underlying romantic nature shines through, adding depth to her character.
Ultimo opens by asking a question he has clearly stopped being allowed to ask, "Come stanno i tuoi adesso?" (How are your parents doing now?), then admits in the next breath "Non te lo chiedo più" (I don't ask you anymore). The rest of the song is what he does with that silence. He leaves the door open, "Ho lasciato il cuore aperto / Casomai torni tu" (I left my heart open / Just in case you come back), and swims out to sea specifically "Per capire che si prova / Ad avere niente intorno" (To understand what it feels like / To have nothing around you), which is a very Ultimo way to handle a breakup: go somewhere empty on purpose.
What makes the chorus land is how small the details get. He hopes the new man "Sappia che cosa c'è nei tuoi silenzi" (Knows what's inside your silences), and then lists her: she dreams about that trip to Africa, she leaves her keys in the car, "Sbrocchi ma sei romantica" (You lose your temper but you're romantic). That last line is the whole portrait, and it is affectionate rather than bitter. The bridge piles up comparisons until one of them stops being a compliment, "Più di un diamante" (More than a diamond), "Delle tue gambe" (Than your legs), and finally "Di più di tutti quei giorni passati zitti sul letto" (More than all those days spent silent on the bed). He misses the arguing less than he misses the quiet.