I'll just make a few brief points:
1. After reading your comments, it appears you're working with a false or erroneous definition regarding allegory and symbolism (or typology). More often than not, you seem to use the terms "symbolism" and "allegory" interchangeably. By definition, an allegory is not literal or real. Symbols, however, can be either literal or not. But you've conflated the two together. Or perhaps mistaken them entirely.
For example, you cited Animal Farm. To answer your question, yes, I believe we can agree the novel is an allegory. George Orwell himself indicates this. Animal Farm tells a story involving talking pigs, cows, and other barnyard animals. The main allegory is an association with communism as it plays out in the former Soviet Union under Stalin. But the story itself is not real. It did not literally take place as George Orwell relates it to us. The talking barnyard animals are not real. There are no real life pigs named Napoleon or Snowball. Or a horse named Boxer in real life. These are imaginary animals created for the purposes of the allegory.
However, they do relate to real figures. Napoleon and Snowball are symbols. Most obviously, they are symbolic of Stalin and Trotsky. But they might also be symbolic of those persons who are Stalinistic or Trotskyite, who share their ideals, temperament, etc. And Boxer is a symbolic of the average working-class Russian proletariat. Or perhaps all proletariats in a socialist or communist nation.
These are some of the differences between allegory and symbolism.
2. Regarding the tree of life and the tree of the knowledge of good and evil:
a. Your initial words on the topic were quite firm that the trees should be regarded as literal trees. But now it appears you've shifted your position to a vaguer one that they could be either literal or literal and symbolic:
I don't see a case either way as to whether the tree of life was primarily symbolic (described as a "tree" in scripture, but actually a kind of, I dunno... a special kind of crop with super life-giving grain?), or both symbolic and literal. In either case, the important truth is the symbolic, metaphysical one: eating of it had "cosmic consequences" - defiance of the natural decay and aging processes.
b. Speaking for myself, I can take the trees as literal trees imbued with Scriptural symbolism.
c. If you take the trees as both literal and symbolic, you've still previously noted you believe Gen. 1-3 to be allegorical. An allegory is not a literal, real life story. What you're saying, then, is you believe in a literal and symbolic tree (which I, too, would affirm), but you believe the tree exists in a passage which is allegorical (which I would deny).
That's like saying you believe Sherlock Holmes is a literal, flesh and blood detective who symbolizes intelligence (or whatever), and who is found in a work of fiction. It's true the Sherlock Holmes stories are fictional, and it's true Sherlock Holmes is symbolic of certain things, but it's not at all true that he is a real life, flesh and blood detective (although he could be based on a real life detective, but obviously that's not the same thing as saying he is a real life detective).
d. Of course, I'll gladly accept if you concede that what you really meant was that Gen. 1-3 should be read literally and symbolically, not as allegory. Because then we'd be in agreement.
3. This doesn't mean that the Scriptures cannot be read allegorically. But the question is, does the text exegetically warrant an allegorical reading?
Again, to take Animal Farm as an example, we know it does warrant an allegorical reading. For one, because its author, George Orwell, has made it known he wrote Animal Farm as allegory. Likewise the form of the book itself is allegorical.
In regard to Gen. 1-3 or Gen. 1-11, however, you've yet to prove your case that the text does exegetically warrant an allegorical reading.
At this point, insofar as I can tell, all you've proven is that there are symbols in Genesis. Adam and Eve, the tree of life, the tree of the knowledge of good and evil, the serpent, etc. are symbolic of certain things. What you seem to have done, though, is noticed the symbolism and immediately assumed that this must then imply the Genesis account of creation is therefore allegorical.
But it's not enough that there's symbolism in the text for the text to be allegorical. The form of the text itself must be an allegory. In other words, you have to demonstate that the text itself (Gen. 1-3 or Gen. 1-11) is an allegory, not that parts of the text make use of symbols.
Again, the question is, on what exegetical grounds do you read read Gen. 1-3 as allegory?
4. Regarding your question about systematic theology:
However, I believe you’re resistance to the allegory and broader symbolism in God’s word is likely tied to the culture context of contemporary conservative evangelical Christianity. You’re exegetical assumptions are perfectly reductionist, so far as I can see – would you endorse a systematic theology for the Bible? Post-enlightenment? I think you are approaching the bible from a post-enlightenment cultural context? Do you say you are not? These are artifacts of the Protestant Reformation. If you would consider yourself “Reformed”, then you’re very much approaching this from that angle, I suggest. But no matter, I don’t know if you subscribe to Reformed theology/exegesis or not. You haven’t said, or if you did, I missed it.
However, the “no argument”, “can’t be”, “perfectly lines up” clues are definitely there, as I see it, that you bring a set of expectations to scripture that are reductive, exhaustive, and systematic. That’s no more perjorative than saying you’re “Reformed”. That’s not an epithet at all to Reformed people.
a. Would I "endorse a systematic theology for the Bible"? I would endorse understanding the Bible on its own terms, in light of how the original author(s) would want his target audience to understand his words, and forming a systematic theology out of this.
b. Yes, I happen to be Reformed in my systematic theology. But I don't necessarily allow my systematic theology to dictate my exegesis of Scripture. Actually, it's the other way around. One's exegesis of Scripture should dictate one's systematic theology.
c. It's true I bring a set of expectations to Scripture. As I just mentioned, one expectation is that Scripture should be understood on its own terms, in light of how the original author(s) would want his target audience to understand his words. Another is that Scripture should be internally consistent as a whole.
Among other problems, your position that Gen. 1-3 or Gen. 1-11 should be read allegorically is inconsistent with your position that the tree of life, the tree of the knowledge of good and evil, and Adam and Eve (possibly) literally existed.
d. But you, too, bring a set of expectations to Scripture. Whether you realize it or not, you're also working with certain assumptions and expectations when you approach the Bible. Such as that certain parts of the Bible should be read as allegory without argument. While I don't doubt that certain parts of the Bible can be read allegorically, if they should be is another question which depends on whether the text warrants it.
But without an exegetically sound argument for why Gen. 1-3 or Gen. 1-11 should be read as allegory, you're at best only engaging in a ruse. It's all smoke and mirrors.
In short, you've not proven on a fair exegesis of the text that Gen. 1-3 or Gen. 1-11 should be read as allegory. You've only assumed it should.
5. I see Steve has weighed in on the topic. His thoughts are well worth considering.