A person feels suicidal when they cannot see any purpose in continuing with their life. However, a Muslim is taught that this life is a preliminary part of existence and one in which we sow the seeds for harvesting in our more expansive and richer life that will follow.
I have read the wording of your question and respectfully, I would suggest that you are making incorrect preliminary assumptions which are then leading you to conclusions that don't make sense, as you say.
You are mistaken when you say Allah is "supposedly just." He IS Just. Consequently He would never oppress His creation. Therefore there is purpose, meaning and benefit in everything He puts us through in this life, even if we don't always understand it at the time.
You are also mistaken when you state that "Allah decides to torture". Allah is Merciful and Loving. He is far above torturing anyone. The trouble is that a person who contemplates suicide has given up on his faith in God, and consequently he risks losing the vehicle (iman) by which he can transfer his good acts into the next life. It is this that condemns him to hell, and nothing else.
Difficulty in this world is a reality for many people, but if they place their faith in God and try to understand His system of creation, they will be able to cope with the trial without thinking of suicide.