Lowering the bar can be difficult in the snatch, espcecially when the weight gets heavy. If this is the case, you could alway just drop the weight (assuming your using bumper plates). By doing this, you'd lose out on the eccentric contraction which comes from lowering the weight but you'd be able to do the whole lift.
As for the number of sets and my previous suggestion about upping your volume, I misread your post to think you were only doing 3 sets. I think the 5 you 're dong is sufficient but I personally like to do 7-9 sets of lower reps for the OL even when the intensity is relatively low.