This is incorrect. Just purely in terms of logic, if God is both omniscient and omnipotent, it follows that His omnipotence also permeates all things. Each attribute assumes the others. They are simply different facets of the same All-ness.
Also, nothing created–nothing which is not God Himself–can be sustained by itself apart from God. Creation is in all ways sustained, rather, by His perpetual will, down to every first and last particle. It cannot be any other way. This is a necessary condition of existence within God’s All-ness.
That humans may sin, rebel against God, and commit acts of evil, does imply that God in any way suspends His omnipotence or His will. His desire is for us to do good, to will what He wills, and to glorify Him; yet part of His will is that we be allowed to choose. We can choose because He wills it, and so, as with existence, the ability to choose can thus only be sustained by His perpetual will.
Although understandable, it is a misunderstanding of terms on the part of meltzerboy2 to propose that God does not have direct control over the choices we make. It is not that God does not have direct control. That we have choice at all is because God wills it, so in this sense, God always has direct control. Rather, It is a necessary condition of providing us with choice that God not choose for us; not because he can’t, but because it is a logical impossibility for both to be given a choice and for God to choose for us.
God created us as subjects. Two subjects cannot simultaneously act for one or the other. As subjects, they are distinct identities. When one subject acts, it acts always as itself, not as the other, or else it ceases to be the subject that it is, which is an impossibility. Subjectivity is intransgressible. Thus if we are to be able to choose our path, God must not. Yet if God chooses our path, we would cease to be subjects and we would cease to have choice.