First, I'm surprised. I had assumed that you were someone that wasn't able to come up with an argument, but apparently I was wrong. I'm impressed.
However, I must disagree, and I'll explain why:
Sure, if he'd fall and wouldn't be able to save himself, he would die, but however, for someone who can levitate, it shouldn't be a problem at all. [
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] Using this ability is exactly what Nagato would have done, if he hadn't been under the control of someone else, who wasn't familiar with all of the Rinnegan techniques and lacked experience in using it. Nagato himself wouldn't have been harmed by the fall if he was in control.
Another thing which you mustn't forget is the fact that Nagato wouldn't be too damaged even if Itachi hits him. He can sense it, meaning that he knows it's coming, and would simply be prepared to use the Shinra Tensei. Sure, the flames would hit him, but what damage would they do if he simply Shinra Tensei's them off a millisecond later ? Not much, especially when he could regenerate later on by absorbing Itachi's other attacks. Your example with the gun doesn't work, as the fire doesn't instantly disintegrate the opponent. The fire wouldn't do too much damage if it's removed almost instantly, and since Amaterasu takes a lot of toll on Itachi, he'd end up losing more than Nagato by using it. He also wouldn't have lost his arm if he had removed the Amaterasu instantly.
I should also add the fact that he didn't sense them inside the cloud due to him being completely under Kabuto's control.
And sure, obviously Itachi wouldn't be harmed by the Chibaku if he prevents Nagato from using it, but I honestly don't see that happening. A common misconception on this base is that the Chibaku takes a lot of time to charge up, but that's not true at all. You can see that Pein starts creating the Chibaku when in the air, and it has formed before he has even landed. [
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] So I don't really see Itachi preventing him from using it.
And if he Amaterasu's the Gedo, it might counter it, but don't forget Nagato's other summons. Overall he's got like 9 summons, along with Cerberus, who so far, hasn't shown any limits on how much he can split himself up. Itachi doesn't have the stamina to constantly use Amaterasu, especially not when Nagato can simply revive his summons.
The Chou Shinra Tensei would still do damage, even if he has his Susanoo up. The Susanoo is a great defense, but since a normal Shinra Tensei managed to break every single bone in a being as large and strong as Gamabunta, along with the other two toads. The damage received from a Chou Shinra Tensei would be even more severe, and even if he might survive, he'd still be heavily injured.
And the neg rep was due to the fact that aside from this comment, almost every single comment revolved around talking about things that happened in their last battle where Nagato was being controlled, even those things wouldn't happen in a fight where he isn't being controlled by someone else. It was nothing personal, and it was not simply due to you disagreeing with me. It was due to you not having really brought up any valid points supporting your opinion, while insulting other users for theirs.