I think that this foreshadows the fact that everyone in Antonio's life has a sin that's holding them down like chains of iron. I think that this also hints towards the loss of his innocence completely. It's very probable this will lead Antonio to want to becoe a priest in his future.
In this scene of the dream, Antonio sees the church being crumbled and the whole town collapsing and I think this foreshadows/ reveals how Antonio's family is breaking apart and how important faith and religion is in his life. This can also foreshadow the questioning of his own faith.
In this scene it shows that the Trementina sisters using Antonio's fears against him. This foreshadows the fact that people will use his fears to instill fear into him and make him fear people like Trementina and other peole that don't like Ultima and Antonio's family.