Here's the thing about Voldemort's will. We are never given an example of it being strong, he can't win the linked wands thing in Book 4, he can't figure out that Snape is lying to him (didn't you say he's the worl'ds most accomplished occlumense and ligimense? That's not a really impressive track record for mental magic, come to think of it, where in the books does it say that anyway?). Heck, in Book 7 he can't even keep Harry out of his head, despite the fact that he managed it earlier. Snape didn't even have Boy of Destiny...(cymbols) shields or anything, but he still managed to lie to Voldemort for years and was never caught. Heck, Voldemort's not even the greatest wizard ever, he consistantly performs worse than Dumbledore, and is only described as "the greatest dark wizard in a century". Again, not the greatest ever everywhere character that Ditto makes out. Since I can't think of an example of him ever beating another character in mental combat, I am forced to conclude that Voldemort does not have a particularly strong will. Hence the sheer terror of Sauron's presence will cause him to curl up into a ball and cry for mommy.

And yes, he is afraid of the dark, it says so right in book 6, during the lake episode with a disturbing similarity to the pool under the Tower of High Sorcery in Palanthas from Dragonlance Chronicles.