I agree that God's omnipotence is not limited by man's will whatsoever. If God wanted to wipe us all out or save all of us, He is fully and completely absolutely Sovereign. Nothing outside of Himself can or will ever limit Him. Nothing created by Him can ever overpower Him. That is impossible.
God is not prevented by man in the slightest. God's desire isn't subjected to man's choice--as if God lost control to man. God's desire is subjected to each individual's choice, because GOD--who is absolutely Sovereign--CHOSE to allow it to be that way. He CHOSE to allow it to be that way, because it brings Him more glory to have willing worshippers rather than pre-programmed robots whose decision to worship Him is not by choice but by ordination. (John 4)
Hypothetical Example:
If I made you: Then, if you would worship me, because I made you in such a way that I built into you that you must worship me, it doesn't bring me any glory. It is meaningless. I created you that way and I know it--even if you don't realize that. If I line up a whole bunch of robots that I pre-programmed to worship me. I know they aren't choosing to do it, because I pre-programmed them to. God is much more intelligent than I am. He would certainly know if He was getting the only automated response those He enabled were capable of giving Him. If that were true, how does that bring God glory?
In contrast, if I could figure out a way to give those robots their own self-contained conscience with which they could choose a course of action--so they could choose to worship me or choose to reject me--then, when one of those robots did worship me, it would mean something to me. That robot had a choice and with that choice chose to worship me. I would be more glorified by the one who came back to worship me than by the 99 who were just pre-programmed and never chose me. The number of creatures following means nothing if they don't have the ability to choose to follow.
Jesus Christ subjected His will to the Father's. Does that reduce His glory? Jesus Christ said the Holy Spirit was greater than Him, does that reduce Jesus Christ's glory? When Jesus Christ said "Do you not think I could call legions of angels" or when Jesus was asking the Father if there was another way, but coming back to "Not My will, but Yours be done"--do you think that somehow reduced the Father's glory one iota that Jesus could have made a contrary choice? NO! The fact that Jesus chose to willfully and wholly subject Himself to the Father's will is an amazing testimony to the glory of the Father.
You really ought to reconsider where you stand on that issue at least. You have been sold a lie. God's glory isn't reduced by people having the ability to choose Him. It is actually the opposite--it is increased!