Is suicide an act of disbelief (kufr) or a major sin? And will God hold me accountable for it, despite the difficult circumstances I am experiencing, such as financial hardship, accumulating debts, and despair with life?

One must be wary of evil thoughts that indicate a poor opinion of Allah. One must be patient with poverty, for the world was only withheld from the righteous for a good reason, and Allah may have intended goodness and reward through that patience. Allah's bounty is vast, so ask Him of His bounty, rely upon Him, fear Him, and obey Him. Do not worry about tomorrow, in accordance with His saying, the Most High: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect." Suicide is a grave sin, and Allah has promised severe punishment to those who commit suicide. The suffering of this world is lighter than the suffering of the Hereafter.