Make copies of your reviews and other feedback. Then politely tell them you will be leaving on the date you originally notified them.
Also, you may want to make posts on Glassdoor.com, jobvent.com or other sites that allow you to anonymously provide feedback on the employee experience with specific companies.
Our understanding has zero bearing on reality. The fact that your conscious of your existence is notable, but does not alter the fact that you exist.
The questions are then just questions about what we can and cannot know... and even then, without complete knowledge of all time and space we cannot be truly certain about anything, so we really just ask questions about what we have seen and learned, make propositions based on that learning, and make decisions based on the reliability of those decisions. In all of that, there is still reality, and as time progresses we face the reality of our decisions.
Plato's Cave illustrates our predicament... we watch the wall from our viewpoint and believe what we see and understand is real. We construct language and thought patterns based on what we see and how we understand it, and yet there may (and in the case of Plato's cave there is) be a greater reality beyond what we see.
Subjecting reality to the logical and linguistic constructs we've deduced from experiencing reality is useful, but not definitive.
We then fall back on having to use what we have learned to determine how the universe is... no answer is provable... we simply make the best decisions we can based on the information we have. Some may believe that a man born 2000 years ago is the Son of God, is God, and has told us about what will was and what will come... others might believe we're in a karmic force and that good and evil struggle for control of existence... others may believe the whole conversation is pointless and refuse to even think about it or discuss it. Either way... as time progresses the truth or folly of their choices will be proven out (although it's certainly possible that no one will know or care).
I think agnosticism is a comfortable and perhaps even logical philosophical position to accept in that it requires no faith, just existence. The hope for an agnostic is that their choices are not in conflict with reality.
Your argument against creationism based on the idea that you can't have something from nothing fails under your logic for agnosticism. One could be agnostic as to the origins of god/God/gods/force/universe (I'll call this thing God... it depends on your religious/philosophical views what terms and understanding are applied) and use the same basic argumentation you used for the universes existence.
A Christian creationist might argue that God existed, that his being defined the concept of existance and that out of that existence something else was created and that thing was our universe... our little closed box of existence. I think we'd agree that if you existed in a closed system you cannot know anything about anything outside of that system (even whether there is or is not anything) without information from outside of your system being made available to you. This is the typical religious argument... that God has made Himself (or whatever) known in some way. The test of course is how reliable are the claims, are the based in knowable reality, are they somewhat testable, are the claims consistent, etc...
The key point in all of this discussion is that our inability to know has no bearing on the actual truth of the matter.
Life is a healthy respect for mother nature laced with greed.