One of the Devil's biggest lies: "I don't exist".
This statement was popularized by movies such as End of days and that other one with Anthony Hopkins.
The Spiritual realm is as real as ours, not seeing it doesn't negate its existence.
Satan and his cohorts rebelling, exercised their will and rebelling did cause changes, negative ones in the Spiritual Realm.
One thing that is true that if you don't understand, it will wreck your faith. You can't understand everything about God, not on this side. Our supposed intellect, our pride is fighting against submitting to God, truly trusting Him and His word.
If we pick out what we want to believe from His word it all becomes meaningless.
The Spiritual war we are in has very real losers, it's a battle for God's truth and Satan's lies. His lies are meant to kill and destroy and that is exactly what they do! God's truth and love save, the exact opposite. The ear will end and God does win the war, but Satan is winning battles with every life that stays trapped in his darkness and lies and ultimately Hell.
Is this the only way that true love could be created between us and God in a glorious union? I don't know, but it is the reality of the situation, our situation that is filled tragedy all around and the beauty of the love of created between us Our Father and Jesus shared through the Holy Spirit.
If you look at testimonies of one of your cohorts Padre Pio, and others like the Warrens, you will see the Devil has not covered His tracks good enough, he undoubtedly is real.
Well that if he exists, then lets make sense of the theology. Up to this point, not one person has been able to explain how Satan managed to sin up in heaven and how heaven did not get the same results as the earth. How can Satan be labeled as evil, when mankind exists? We have done more evils than he has by a long shot and for a longer time.. he is only brought in because we are too narcissistic to take full responsibility.