AKG wrote:
1. In regards to the claim whatever is changed is changed by another I've heard atheist claim that gravity refutes this.
Well, it doesn't.
Seriously, in order to say any more than that, we'll need an actual argument, or at least a summary of one.
If it's that two objects interacting gravitationally (orbiting one another, say) are supposed to be a counterexample, then the second most important problem with it is that each object does exert a force on, and impart motion to, the other. The most important problem is that the entire system still needs a Prime Mover to set it in motion in the first place.
AKG wrote:
2. Would humans and animals also refute this claim as when I get up to walk I don't think something that is already walking makes me walk.
Right; parts of you that are already in motion impart that motion to other parts of you. So no.
AKG wrote:
3. I've also heard some atheist say that a quantum vacuum actualizes itself in the same way that humans in the example I states above and it does not need something outside of it to actualize itself.
Here again, we'll need to know more about what the argument is in order to identify where it goes wrong. But if it's much like the previous example, then the problem will be that it really involves parts moving other parts.