I have some questions for these.
For Echo of Will why would physical weakness have any bearing on a person's ability to resist Qayin's spells? In any case, with regards to a strong or weak mind, I think you are more or less saying that a strong-willed person who doesn't follow orders is more likely to not do what he says, correct? Also, how is the ability affected by those who have barriers against mind control/mental tampering?
As for Flesh Animation he can only do this on dead organic matter, correct? As it is, this ability is rather strong for a simple ability, given that Qayin could be running around with a grizzly bear-sized monstrosity for an indefinite period of time. Perhaps you could reduce the size of his construct to about the size of a single human, or otherwise nerf it by placing a time limit on it or making the construct really janky and hard to coordinate, or else placing a distance limit on it (eg. stops working if it goes more than 50 feet away from Qayin)?