Soluçava is the imperfect past tense of the verb soluçar, meaning 'to sob' or 'to hiccup'. It's a poignant word that conveys deep emotional distress.
In the context of the song, it highlights a moment of profound sadness and disconnect in a relationship: "Enquanto um de nós soluçava, o outro fingia dormir" (While one of us was sobbing, the other pretended to sleep). This word captures the raw emotion and the painful reality of a love in crisis, making it particularly impactful and memorable.
This is a song about the morning after a bad night, when two people who love each other have gone quiet on each other.
The opening image says everything. It hurts to sleep with your back turned to someone you care about, someone you already gave your heart to. One of them was crying in the dark and the other pretended to be asleep. The singer calls that silence worse than any argument, because an argument at least ends.
So when he sings "vamos acabar com isso", he is not asking to end the relationship. He wants to end the coldness. He admits he has no nerves of steel, asks her to come and hug him, and offers to call the whole thing a draw, zero to zero, with nobody keeping score.
The last part is his reason for wanting it back. There is no deeper love in this world, she is the owner of his being, and nothing is more beautiful to him than seeing her smile after a night together.