This may have been asked previously, but was he just dreaming/imagining everything? The last shot is of him on the beach holding the woman made of sand from the beginning of the film. That same shot was used in the beginning as well. Just curious!
It comes full circle. If you notice in the beginning, Freddie simulates having sex with the sand woman. Next scene, he is seen jerking off into the sea. Then he goes to relax and chill with the sand lady. At the end, he finds a woman, has sex with her, but isn't seen cuddling with her but with another sand woman.
Obviously, a bit more than just Freddie being Freddie could be interpreted.
I think he is stuck in his old ways of not being able to have growth in his relationships. Because of his past relationships and how he was brought up, Freddy lacks discipline to cope with other people and their opinions. He's constantly on edge always expecting something to go down. Because of this, he finds no peace but with an artificial creation of a woman who can't react back to him.
Why would anyone care about Freddie, except that we are just trained to get into caring mode when we think someone is the star or the movie, like we root for two people to romantically get together, who are probably better apart.