Peace,
ALLAH has been called al-haqq throughout the quran. That is, truth of the highest degree. His command/speech is truth (3884). Iblis did not accept his command/speech/truth (3874) and this act turned him into a rejector of truth. Firon's magicians accepted the truth when it came to them, when they were before rejectors. You cannot fault this interpretation because if ALLAH is indeed the truth then there is literally no way it can be wrong. As for the rest of the terms, a cross reference of these verses is all you need to clarify their meanings.
Why the truth interpretation? Because the idea of "believer" and "disbeliever" requires faith and faith is gambling on ignorance which is prohibited (1736). For such a thing to matter there is the assumption that there are many possible religions/truths/systems that all likely could be true. Is ALLAH uncertain about his creation?
Now if ALLAH knows for himself that He is the highest truth and his system is assured truth & justice, and that there can be no fault for those who follow his path of obvious and clear truth standing out from error, then why would his most esteemed people (mumin) be a bunch of people thinking "Yeah.... I'm kinda hoping this is all true"? Because that is what "belief" is!
Rather, the mumin are certain to meet their creator and they know how, why, when, where, they know the details, there is no room in their hearts to turn back. Can you turn back to thinking 2+2=5 after you know 2+2=4? It just doesn't work. "Muslims" are those who have faith, mumin know with certainty.
Key point; the truth can be proven to be true. A belief about higher beings can never be tested because only the true belief exists, the others are all unfalsifiable. Indeed "belief/disbelief" is simply a weaker statement than acceptance/rejection. If you accept/see truth, you believe anyway. If you believe, you do not necessarily need to see truth, you can hope/imagine it's there. How useless!
Let me try to understand what you're saying, please clarify are you saying that Allah is "that which is in accordance with fact/reality"? Like the reality behind a specific event would be Allah?