Does expelling gas while uttering the name of God, or mistakenly attributing the characteristic of injustice to Allah, the Exalted, constitute an act of disbelief?

You are suffering from waswas (whispers/obsessive thoughts), so cast away all these waswas and do not pay attention to them. None of what you mentioned is considered disbelief (kufr). "Al-Jabbar" (The Compeller/The Restorer) is one of the beautiful names of Allah, and its meaning is the One who rectifies the affairs of His creation. It is permissible to describe a created being as jabbar, as in the verse: "And they sought victory, and every obstinate tyrant was disappointed" (Quran 14:15). These are waswas that must be ignored.