You fail to understand what scientists know versus what they speculate about.
Not really. They're very clear about that. It's a requirement of science that you enumerate all of your assumptions, and quantify uncertainties whenever possible.
Making the assumption that they are even somewhat accurate about the big bang (unlikely)
For example, that's not an assumption. The general idea behind the big bang, that the universe was once infinitely small and it expanded, can be used to make certain predictions regarding what you expect to see when you look out in all directions, what you expect to see in the CMB, etc. You can precisely measure how accurate those predictions match up with experiments, and it's really, REALLY accurate.. Check out the text that goes with that graph: "Graph of cosmic microwave background spectrum measured by the FIRAS instrument on the COBE, the most precisely measured black body spectrum in nature. The error bars are too small to be seen even in an enlarged image, and it is impossible to distinguish the observed data from the theoretical curve."
What that boils down to is that your statement about how unlikely it is that scientific theories are "even somewhat accurate about the big bang" is provably an incorrect statement, based on our best available measurements. If you want to make an argument for your case, you need to bring something more to the table than, "I personally feel like scientists are speculating and can't possibly have a high likelyhood of stumbling upon what actually happened." The people you're criticizing have data. You have a feeling. You need to bring in some data, at which point I and everybody else will be glad to accept that our previous theories were wrong. The Lumineferous Ether was accepted theory, but when Michelson and Morley couldn't detect it using their inteferometer, and Einstein showed up with special relativity as an alternative with supporting data gathered from the 1919 solar eclipse, the Ether theory was destroyed. Scientists do not fear being proven wrong. However, you do have to bring evidence with you.
Everything is just speculation from unimaginative scientists who think they know what happened 14 billion years ago at some random spot that they can't even point their finger in the general direction of.
See? You're criticizing a theory that you don't even understand. Scientists can point to you the spot the Big Bang happened, exactly. So can I. It happened where I'm standing right now. At the exact spot that I'm standing. It also happened at the exact same spot you're standing. And at the exact center of the Andromeda galaxy. And exactly at whatever spot you pick at the edges of the milky way. Or any spot at all in the universe: Every spot in the universe is the center of the universe. The Big Bang isn't matter spreading into existing space. The space in which matter exists is expanding. Check out that video, it explains it really well.
That does not mean that space was not infinitely large while at the same time infinitely small, its all a matter of perspective. Outside looking in, its infinitely small, inside looking out its infinitely large.
This right there is the difference between speculation and scientific hypothesis. "Something that looks small from one perspective can look big from another perspective, so whose to say what's infinitely small or infinitely large" is hand-waving. Scientists don't do that. They tell you what they mean by small, and when. At roughly 10^-43 s after the Big Bang, the universe was 10^-35 m. That's the end of the Planck Epock. During the Inflationary Epoch, the universe grew to about 10 cm by 10^-32 s. These numbers are, admittedly by everyone, highly speculative, because there's no good theory of quantum gravity at the moment. However, using the laws of physics as we currently understand them, those numbers are arrived at. With actual formulas, with numbers arrived at through actual measurements. What do you have for your hand-wavering?
Note: We can't get an accurate police report 20 minutes after the event with 20 eye witnesses, but many are dead set that we KNOW what happened during the big bang. When you think about things like this, use your head and think about the police report.
That's because eye-witness report is highly unreliable. It's the worst way of gathering evidence in existence. Human memory is malleable, it's flawed. That's why when we convict people of crimes, we try to gather evidence using science. Recorded video, fingerprint dusting, DNA matching, ballistics. Those scientific tools are actually highly reliable. You know, the same tools we use to probe the origin of our universe.