One point RE: Counterspelling. The Balrog counterspelled Gandalf's spell of closing on the door to the Chamber of Mazurbul after it was cast, not while or before the casting. This tells us that for purposes of LOTR counterspelling, spells that have already been cast can in fact be countered. Hence Sauron can lock Voldemort down hard magically, then crush him in the maner he finds most pleasing.