Your "bold prediction" is unwise. First, it places you front-and-center in the healing event, not God. You have oriented the spotlight upon yourself by making God's potential healing of somebody all about what you believe and how strongly and what you'll do if healing doesn't happen. If God decides to heal, you get to steal some of His glory by having made the healing about your prediction and your resolve to quit CF if He doesn't heal. As far as I can see, your "bold prediction" is just ugly Self attempting to insinuate itself into God's business.
Secondly, your prediction presumes to dictate what God will do. Your thinking seems to be that the strength of your certainty that He will heal obliges Him to do so. There is no "thy will be done" in your prediction, but only "my will be done."
See here how you're making what God might do all about you? You're going to prove that God heals. Well, God doesn't need you to prove anything for Him. He's quite capable of proving what He likes without your self-aggrandizing "predictions."
It doesn't really matter what you believe God will do. It only matters what He wants to do. The strength of your belief about healing doesn't have anything really to do with whether or not God will heal. God will heal a person or He will not; you are not the linchpin in how He decides.
What does Satan have to do with the fellow's tinnitus and hearing loss? Our bodies break down in all sorts of ways simply because we live in a world corrupted by sin. Death and disease are not typically demonic in origin but merely the consequence of our own wickedness.
And the devil just laughs at this sort of thing. You have put yourself in the limelight where God should stand and the devil applauds. And if God should choose not to heal you have made a foolish, unnecessary vow that your pride will bind you into keeping.
The "healing" obtained through Christ's stripes is a spiritual one, not physical. By his stripes, the rift our sin has caused between Man and his holy Creator is healed. This is what is in view in Isaiah 53:5, as the very next verse explains:
Isaiah 53:6
6 All we like sheep have gone astray; we have turned every one to his own way; and the LORD has laid on him the iniquity of us all.
See? We have strayed from God, turned to our own way, and so caused a fatal separation between ourselves and our Maker. Jesus has come to reconcile us to God, to heal the rift our sin produced between God and us, not heal tinnitus. Now, of course, God can heal but He makes no promise whatever to do so any and every time we may ask Him to. And so it is we read of Epaphroditus falling ill and not being healed by way of supernatural miracle; we read the same thing of Trophimus and Dorcas (who actually died); and we read of Paul telling Timothy to take wine for the sake of his stomach rather than claim healing in the atonement.
