There are three categories contained in your list. There are miracles in the Bible in your list, there is one thing in your list which simply is not in the Bible at all, and there is a statement which is probably metaphorical, not literal, and therefore which should not be problematic for this reason.
1. In category number one is talking snakes (actually only one talking snake–singular, not plural), and a talking bush. First of all, the bush was not talking, but the bush had flames in it and God spoke from the bush, it was not the bush speaking.
The talking snake and the flames and voice in the bush are examples of miracles in the Bible. If one assumes that miracles cannot happen, then obviously these things did not happen, but if we do this, then we are applying circular reasoning. Here is the reasoning: Question: Can it be true that a flame can be in a bush and a voice come from that bush? In other words, can it be true that supernatural events happen?
Answer: We know that supernatural events do not happen, therefore these things did not happen.
This is assuming the answer before asking the questions–it is circular reasoning–which is a logical fallacy.
Here is how I would deal with this question. I would ask the atheist to assume, just for the sake of argument (not to actually assume this, but just to assume it for the sake of argument), that there exists an all-powerful, all-knowing, omniscient, omnipresent God. If this were the case, could that God make a snake talk and make a bush have flames without being consumed?
The answer, of course, is Yes!
Well, then, what remains for us to do is to investigate whether the evidence leads to a reasonable conclusion that miracles do in fact happen. But to assume it cannot happen a-priori is to reason falsely. Let us study the Bible to help determine if in fact miracles do happen.
You can go from there by looking at the statements of Jesus, the reliability of the witnesses, the evidence for the resurrection and so forth.
The key thing is that the atheist’s argument is a total logical fallacy.
2. Now, if it were true that the Bible talks about unicorns, that would be extremely problematic. This would not be a claim of a miracle. It would be a claim about the natural world which is simply not true. It would be an example of a biblical myth. Here is the resolution to this problem. There are no unicorns in the Bible. There is a unicorn in the King James Version (for example Isaiah 34:7), but this is a bogus translation. It is not even weakly supported by any manuscript. There is simply no justification for this in the biblical manuscripts. There are no unicorns in the Bible!
3. As for the six days of creation, from earliest times, Jewish and Christian theologians took the first chapter of Genesis to be a theological treatise, not a “scientific” one. The “days” are episodes or periods of time. Either that or they are categories of what God did. There is the day/age model and there is the framework model. Which is the correct one is debatable, but few scholars take these days to be literal 24-hour periods of time. Therefore, the fact (and it is a fact) that scientific evidence does not agree with creation in six literal days is not evidence of biblical error but evidence of the fact that certain people take these days to be literal. That is their prerogative, I suppose, but the majority of scholars, including scholars before the dawn of the scientific age, have not taken these “days” to be literal.
I hope this helps.