bit of spoilers...
the 3rd tl is basically a world where kloff is the one who regressed while aeroc is still his "beautiful, untainted" self with no memories of the previous life. i don't remember much anymore bcs it's been years but it's funny how aeroc treats him like a crazy person (bcs he acts like one). while they're still kinda toxic, kloff isn't as bad as in the first life since he learned his lesson the hard way. he also had ptsd about aeroc going into the alleys so that's fun.
as someone who can't forgive kloff, this world makes me smile bcs while aeroc gets his happy ending (no memories of abuse, plus he gets together with his love at first sight), kloff is basically rotting from the inside bcs he knows he can never apologize to the aeroc of the first life, nor can he say "i love you" to that same aeroc. all he can do is love the current aeroc with all his might.
this story can be seen as having both a happy ending and a tragic ending at the same time

Read all that. Still hate Kloff. He's inexcusable.
That said, for the sake of my own sanity, I've come up with a way to rationalize him. Maybe not what the author intended, but once a story is out in the world, readers are free to interpret it however they want.
Basically, I view the second timeline as a reconstructed world rather than the original one rewound. The people carry over memories to varying degrees, but they're not quite the same people anymore.
That's the only way I can make sense of this story. First-world Kloff was a complete asshole. Second-world Kloff feels fundamentally different. Same with Aeroc. Aeroc remembers everything, so his past and present selves have almost merged. Kloff only remembers fragments, so the old timeline barely shapes who he is now.
So yeah. The mental gymnastics I do just to justify all the time I've spent on this toxic story