How does Montresor use reverse psychology on Fortunato?

There are many reasons that the author has Montresor keep suggesting that they go back. Perhaps the most important reason is that it will make Montresor seem perfectly harmless to Fortunato. If Montresor keeps suggesting going back, then he can't be leading him anywhere that could be dangerous.
But Montresor knows that Fortunato could easily become suspicious. Montresor is taking him a long, long way through a network of dark passages. Why on earth should he have stored a big barrel of wine so far away from the bottom of the stairs leading down into his wine cellar. The farther they go, the more strange it must seem. The "pipe," if it existed, would contain 126 gallons of wine. That is a huge barrel. The men would have had a very difficult time carrying it or rolling it through all those catacombs. It is only because Fortunato is heavily intoxicated that he doesn't protest. Poe describes his intoxication as follows:
He turned towards me, and looked into my eves with two filmy orbs that distilled the rheum of intoxication.
Poe had to have Montresor take Fortunato all the way from the street where he first encounters him back to his palazzo, down into the wine vault, and through a series of catacombs without saying anything about the Amontillado. It would seem natural for Fortunato, who is supposedly an expert, to ask questions such as "Where did you get it?" and "How much did you pay?" But Poe didn't want to Fortunato asking questions. Fortunato knows more about Amontillado than Montresor; otherwise Montresor wouldn't be asking his advice. If Fortunato started asking questions, he would probably sense that Montresor was lying. Poe himself may have known nothing about Amontillado except that it was a gourmet sherry and was an important export from Spain.
Instead of talking about that which is the object of their trip, the two men engage in chit-chat about the Masons, family crests, the nitre covering the walls of the catacombs, and other miscellaneous subjects. One of the ways Poe fills the gap with dialogue is to have Montresor keep suggesting that they go back. For example:
“Come,” I said, with decision, “we will go back; your health is precious.You are rich, respected, admired, beloved; you are happy, as once I was. You are a man to be missed. For me it is no matter. We will go back; you will be ill, and I cannot be responsible. Besides, there is Luchesi—”
Poe seems to be indicating that Montresor is using what is called "reverse psychology" to keep his victim motivated. But this is also a way of filling a lot of space with dialogue.
So Montresor keeps suggesting that they turn back because:
Poe has to fill up some space with dialogue.
The suggestions make Montresor look innocent. He can't be leading Fortunato into any danger if he tells him to turn back.
Montresor is using "reverse psychology" because this is often an effective way to get some people--especially drunks--to insist on doing the opposite. We all know of drunks who insist on driving themselves home just because their friends are trying to talk them into letting someone else drive.
The suggestion to turn back is a distraction. It is beginning to seem ridiculous that they should be walking so far in these bone-filled, stygian catacombs to find a single barrel of wine. Poe is not only distracting Fortunato but distracting the reader, keeping him from asking awkward questions, such as, "Why did you move the wine-barrel way back here?" "Why didn't you just tap the barrel for a couple of bottles and bring them up to your living room, where people could sample the wine in comfort?"