I've stated my opinion on this issue before, but why not again?
Saving the eye that does not see is fairly clearly G'Kar's eye. I very firmly believe that Morden is the man who is already dead -- especially considering how much was made of that in "In the Shadow of Z'ha'dum." Furthermore, if Sheridan had been that man, and Londo hadn't killed him, then he wouldn't have needed the third chance at redemption... and speaking as a storyteller, there's no way he's not going to need it. If you've got three chances and you're fictional, you're doomed to blow the first two. Sorry.
Which brings us to the last... "surrendering to his greatest fear, knowing it will destroy him." I too believe this means accepting the keeper.
Although Londo is fairly ambitious early on, he is honestly sincere (at least by the beginning of S4) in his repeated assertion that all he wants is to serve the Centauri people. His willingness to sacrifice his life to avert the Vorlons is more than enough evidence of this. So, bearing this in mind, what is Londo? A misguided servant, trying to do the right thing but too often failing. To betray the Centauri people would be crushing. This, of course, is more or less what the Drakh are asking him to do. It's a bitter choice: sell out your planet or we kill millions of your people. So in one way, bowing to the Drakh is an act of self-destruction for Londo.
In a more personal way, Londo has cherished his freedom and his power. He has come to realize that he always had power, that he always could have done something (he came to this conclusion, I believe, in "The Very Long Night of Londo Mollari"). Submitting to the Drakh will rob him of all that power, and finally, after all that time of him saying "I have no choice," he can say it with absolute truth.
Finally, and probably most significantly, when Londo has decided to accept the keeper but has not actually done so yet, he goes and talks with G'Kar. In the course of their conversation G'Kar finally forgives Londo -- and Londo needs G'Kar's forgiveness more than anything else. Londo's concerned by what he may have to do under the influence of the keeper, but G'Kar, not knowing the problem, reassures him and says that he believes Londo is a good person trying to do the right thing.
If G'Kar believe that Londo is redeemed at that point, and can in fact forgive him for the first time, then I believe Londo's decision to accept the keeper is his third, final, and successful shot at redemption.
