How does "The Cask of Amontillado" comment on psychological freedom and confinement?
You have certainly identified that psychological freedom and confinement are key aspects of this masterfully gothic tale. It is worth thinking about the kind of writing that Poe produced before answering this question. Poe was known as a "Dark Romantic", which means he was one of a group of authors who focussed their work on the dark side of humanity - evil, sin and the capacity within us all to do terrible things.
Clearly, this becomes a useful context in which to place this story. We are introduced to a narrator, who, we go on to suspect, is unreliable, in that we begin to doubt what he professes to us. Consider how the story begins:
The thousand injuries of Fortunato I had borne as best I could; but when he ventured upon insult, I vowed revenge.
We begin to wonder about the accuracy of the narrator's perception when we see the trust that Fortunato displays to Montresor - if he had indeed, "ventured upon insult", he might not have been so quick to fall in to Montresor's trap.
It is clear that we are seeing the narrator beneath his mask of public respectability. The setting of the story is key in this respect too - it is set during carnaval, when characters wore masks and fine clothing. It is perhaps ironic that Montresor chooses this time to reveal his true inner self.
Note too, the symbolic function of the catacombs. Consider how they are described:
We had passed through walls of piled bones, with casks and puncheons intermingling, into the inmost recesses of the catacombs.
As Montresor leads Fortunato on into the ever-deeper depths of the labyrinthine catacombs, we as readers are treated to a special voyage into the psychological state of Montresor - the deeper we get, the more devilish, sadistic and horrific his thinking and actions become. It is key that Montresor commits his heinous crime once they have penetrated the depths of the catacombs and reached the finish - he is able to express his psychologically disturbed state to the extreme. Yet, to return to your question, I wonder whether the bricking-in of Fortunato represents the psychological repression of Montresor's evil desires and actions - we can only assume that after chillingly sealing in Fortunato and leaving him there to die, Montresor is able to put on his mask of respectability and operate in Venetian society once more. Having "buried" his unacceptable psychological side he can freely partake of "normal" society again.
"The Cask of Amontillado" by Poe is certainly a story about the psychology of the narrator, and confinement is a difficult element to miss in this story. Your phrase is "psychological confinement and freedom," and that's an interesting concept here. The narrator, Montressor, is clearly suffering from some kind of mental instability. He believes Fortunato has offended him often enough and badly enough that one last insult has compelled him to take this drastic measure of revenge. Fortunato, though, apparently bears him no ill will. He goes fairly easily with Montressor, suggesting that the insult, if made at all, was not delivered with much venom. This over-reaction and internal exaggeration is indicative of Montressor's psychological confinement. Conversely, Fortunato appears to enjoy the freedom of a guilt-less conscience.
On the other hand, Montressor (the psychologically confined) is literally (physically) free at the end of this tale. After all, he says, the only true revenge is getting away with the act, which he does. Fortunato, though literally confined, is psychologically free--from apparent guilt as well as the crime of murder.
This ironic twist is just one of many intriguing components in this story.