I'm glad you mentioned jail/torture scene. That is another obvious clue that shows behelit is source of Griffit's power. He's holding on very well until they take behelit away from him.
Again, Griffith doesn't care about Guts as a person. He cares about him combat prowess. That is what makes Guts special in Griffith's eyes, he's by far the most powerful individual he met on his rise to power (thanks to behelit). That is why he's so desperate to have Guts beside him, he's not sure he can make it without him.
But best proof is Zodd, who never acknowledged Griffith during their short battle and only spared his life because of behelit. Zodd was very pleased with Guts, because only thing that matter to Zodd is search for worthy opponent. He's not even evil, as you can see in the manga. The most powerful apostle and the only one who doesn't enjoy torturing people. If Griffith was talented warrior, Zodd would recognize that in him. He was actually confused why God Hand choose him of all people.
Interesting points, i guess theres not really anything that proves either way regarding the behelit. It did bind his destiny, so i guess in a way he is made to survive, but it could also have chosen him because of his destiny. Since it does seem to chose him, as it returns after the jail scene.
I guess it also served him during the assassination attempt, maybe i overlooked it a bit, but i still dont consider it to retract from his own hardworked success.
Zodd is such a cool character, always a big favourite of mine. I wonder how he actually knows what he does.. but yeah he is confused with why they chose Griffith, maybe its because at the time his position wasnt very high, or maybe he simply doesnt view things as the God Hand does. He is basically only in search of strength and skill, which i believe Guts at that point had exceeded Griffiths. And so he overlooks his tactical skills, and political genius.
That which would make him a good king (maybe) and so fit the role he is put in the latest chapters of his glorious city.
And i believe i read scanlations, and they were all solid. Im not too picky on it, the ones ive read were good. Still considering picking up the books, but they are expensive af. And now the new spines are out for the reprints, so buying them would make for a poor looking collection.