I think he was just hoping for the best. Abel has this way about him that makes him want to make all the people around him happy and to treat every wild creature like an understood being.
He isn't wrong. You can sit with many animals if you know how they work.
He definitely blames himself. We already know because of a reaction he had earlier in the story when he learned the king was battling the whole time. His last words to him was not to trust anyone or something like that.
Then, when he realized he was with his majesty this whole time, he still blames himself because he could have guided him in some way.
He already forgot the time he spent with his majesty as Lil, he gifted him pomegranates, requested that his majesty didn't kill bugs, stopped from killing some people (I think, I didn't give af about them) Told him stories like when the king was younger.
Lil Abel has already has a profound affect on Grown up Majesty. He just doesn't know it yet.
I think Abel wasn't expecting the prince to be all-loving and such. A king can indeed shed blood, lots of them even but they could also have compassion, which Karas completely lacked.
Idk if he blames himself for how the prince turned out or hates how he did. It wasnt his fault but how did he expect him to grow up? He literally saw the horrors of what he went through, he got killed by the people that got left by his side when he died, yet he still expects him to turn out to be a happy and innocent boy? Theres absolutely no such thing as a king without any blood in his hands, much less a warrior.