The arguments you've stated rely upon a somewhat basic understanding of how the universe operates. While I am not a scientist, I will use all of my understanding to assist you.
This is a human-centric interpretation of newton's first law. This cart can not move because I have not pushed it ergo I am the "powers that be". However, it does not take into account quantum forces such as the 4 forces of nature. While its not well understood yet, gravity can act as an independent mover so long as there is sufficent mass to cause movement. We do not watch a leaf fall and say "God did it" because we understand that the tree sheds its leaves and gravity pulls them to the earth. In space, a large gravity well is enough to act upon the motion of a celestial body. Concerning the big bang theory, this can be explained using basic physics: As density increases, so does the pull of gravity. As density increases, so does the pressure between sub atomic particles. Once the force of gravity forces the sub atomic particles to behave in a manner counter to their nature (such pushing two positively charged particles too close to each other), then the particles resist. Gravity is not the ultimate force in the universe (which is why the Voyager I was able to leave our solar system and not fall into the sun), so eventually enough sub atomic particles straining agains the crunch can override the power of gravity. Once that tipping point is reached, the mass starts expanding, gravity is weakened, and the expansionary force is unleashed. A simple counter to this is "Then who caused the big crunch? Eh?", but this is a faulty premise. The simple fact that things exist are a testament to that. Nothing in our universe can be completely static because that would make them immutable. If something exists, even without any deliberate action on its part, it will affect the universe around it.
Newton's first law: An object will either rest or continue moving until acted upon by another object (yes I know, not word for word, but its accurate none the less). So, if I fire a bullet at 50% the speed of light in a single direction and there is nothing in the path of motion that will ever act upon that bullet (no gravity, no particles, no anti-matter/dark matter), then that bullet will travel forever or "ad infinitum" simply because there is no force to stop it.
Based upon the refutation of points 3 and 4, this is not be held true.
Now, an assinine refutation would run as such: "The person who developed this line of thinking can not be held as an honest source because they are not true physicists. They are people who study the peripherals of the field and utilize their own gaps in knowledge to prove their own theories. In a scientific community, ANY theory can be dis-proven by anyone who can present evidence that can be replicated. Hence why gravity is called a theory. The person who wrote this theory can be refuted but refuses to recant an inaccurate statement."