Wonderful story telling! Clark's hesitancy shows he knew full well he had his chance for escape. I'm theorizing that if you were a young adult, taken and captured for 7 years because of your powers, beaten and kept weakened, etc... it would be a ray of golden sunshine to suspect someone was finally giving you small bits of humanity back. Therefore, perception is very important to him. Which has been his character we know him by. As Superman, he has the desire to be seen as helpful, and takes it personally when the public portrays him as anything other than that.
So, he either takes his chance at escape, when he knows the 'poison' is around somewhere and can weaken him, or he takes the chance at showing humanity, and hopefully gaining... trust
Wonderful layers in this story!
