If he does get trapped, I feel like he will break out one way or another because: 'Sister'. I just do not see him leaving her on her own for 10 years.

Watch that shirt not even fray at the seams.

After Elves and Dwarves, I can not find it in me to be surprised. Predictions on the next type if there is one?A Cait Sith may have been cooler to a degree but I find them too off putting with the amount of times they have been depicted as too cute and adorable or massive Edgelords. 

It would absolutely suck in many ways. Though in reality it is actually not that big of a deal outside of cosmetic reasons. For daily life stuff you would just need to adjust and form some habits with depth perception and likely a few other things. Outside of things like sword fighting and the like that require awareness of attacks from both sides, other things like crafting jewelry or detail oriented task really only require one eye. Modern day examples would be using a microscope, reading/writing/typing, painting ...I am actually having a hard time thinking of anything that has a mandatory two eyes kind of limit outside of sports like activities?

It upsets me how deeply I align with this rabbit. I wonder if there will be another one in the next batch of siblings.

Sadly.... it actually does make sense. 
At the very end he had the life that rebirth would have gave him, he just worked for it all, instead of having easy mode throw it in his lap.
He caught some feelings along the way. People that would give their lives for him - I imagine that would be one real dozy of a connection to have.

It is just and ending with out the finality of a permanent ending. (Even if he killed the super Evil Villain and saved the world with sacrificing the "Ultimate Reward") It basically ended with him shifting into "normal mode" without a reason to constant try to have his life ended by proxy. That basically cleared the meaning of the title, Kind of rare that the Author was so on point from my personal experience.

This is really just a twisted story of failing upwards... I almost want to root for his death, but at this point it feels like dying and getting immortality would actually take longer.