fini, i think what he meant was that he couldn't control the ring in the sense that he couldn't stop it from corrupting him. Galadriel herself was afraid of the ring, everyone good was.
but if anyone can use it, i think gandalf would be the most powerful.
as for the balrog using it, when i read the book, my impression of them is that they r animals, acting only on instinct, so they wouldn't even have the idea to get the ring in the first place, let alone use it.
It doesn't matter who possessed the ring, they were all equally dangerous...because they all served the master of the ring, and no one else.
If they could work their own will through it, then possession of the ring wouldn't be a problem...but no one could, all, even the hobbits, will succumb to its rightful owner eventually.
That, is the only danger of the ring, and nothing more, it does not make you strong, or smart, or make you a HE-man...it makes you a slave.