I don't think that Satan "wants" us to suffer at all. At least he has no say in the matter, it's all God's pronouncement in the first place. Satan, on the other hand, accepts than man is fallible, imperfect, and human. God is never satisfied with our impure mortal selves, that's why with him we're always being judged against that perfect period in the Garden of Eden when we weren't truly human.
If anything, Satan is the essence of free will itself: he will always welcome us, no matter what we become in our short physical lives, just as a parent will love their child no matter what they become in life, despite their mistakes and misgivings. Our immortal souls deserve no permanent rejection for the mistakes of a fallible life - a life of fallibility which God sent us to, mind you! So not only does God judge us for being human and our deviations from "impurity," he was also the one who, in his so-called "eternal love" cast us out of his presence in the first place, into that world where we are even able to make such fallible mistakes! And as we have seen, even God is capable of the vices which supposedly condemn one of us to Hell: avarice, anger, even murder, depending on how you look at it.
So in a strange, Phillip K. Dick sort of way, Lucifer is a much better, more loving parent and much better and kinder "person" to us than God, our "actual" father and supposed "perfect being" is.