Yup. In the Epilogue, Victor's body IS in that cemetery, right next to Ethel's ='(
In my mind, Jack and Selina don't have a happy ending, especially not together. Jack looks for Selina to try and hold on to something within himself, that he found while he was with her, but that he already lost. He is now trapped in the same life his father had and that Nicholas was supposed to inherit, which, to Jack, is the worst punishment of all - the loss of his freedom. He is now the leader of the Skeffington's Empire and, by his choice, he plans to keep it that way, since he feels like he deserves it and like he owes it to his father and brother.
Selina will forever morn the death of her siblings and, at the same time, forever hope Victor will come and find her again. Part of her can't deal with the fact that she had her family back, only to lose them all again in such a tragic way. She allowed them to corrupt her and her innocence and she has to deal with that for the rest of her life. In my mind, she spends the rest of her life playing her violin, waiting for Victor to come.
Nicholas does move on and does forgive Jack. But he never returns home. He travels the world, communicating frequently with his mother and Jack by letters, until he eventually builds himself a humble home in a remote part of Spain. Unlike his brother, he refuses to use his family's money for support, he works hard to earn it, learning how to do basic and temporary jobs. He finds happiness in the simple and carefree life he now lives, but he never finds love again, because he finds himself unable to trust. Deep inside, he will forever be in love with Hannah.