No the devil cannot control our dreams however he can instill in us certain tendencies to fear and visions which of course are not found in our dreams but outside of them. For instance the great Divine Mercy saint, St. Maria Faustina, had a vision while she was in bed (she had to be awaken to see this vision), that demons were in Purgatory. Now we know that after death there is no place for the devil to contend with us so the vision must have been placed by the devil to make the saint believe that demons are in Purgatory. In the case of fear while one is trying to sleep the devil can try to install fear in us trying to make us believe this fear is from us or that we have done something so wrong so that we have this fear to make us believe God is not here or caring anymore. This can happen to the best of us. To defeat this strategy of the devil is to simply tell someone what is going in you so that the devil will retreat. The devil hates group therapy and does not stick around when you learn to spill the beans of what he is trying to accomplish in you. So in both cases the devil needs you to be awake. If you are sleeping the devil will wait until you are awaken or in the case of St. Maria Faustina the devil will use extraordinary means to awaken her. Remember too that the devil cannot do this unless he has permission. God will never allow the devil to go beyond what you cannot handle.