And there is no biblical evidence to warrant a belief that [animals] did die.
There is, actually, even if you're not aware of it. I refer you to Psalm 104, known as the Creation Psalm.
There actually is no reason to suppose that they did die.
Again, as far as you're aware. As it turns out, there is an abundance of reason for supposing they did die.
However, there is plenty [of reasons] to suppose that they didn't die.
I would ask you to give me just one reason but, since I know you would refer to Romans 5, let's just go ahead and look at that.
"We are told that death entered our world because of sin," you said, "and everything that would cause death with it."
You are omitting something awfully crucial to this discussion and I certainly hope it was a matter of negligence. What does Romans 5:12 say? "So then, just as sin entered the world through one man and death through sin,
and so death spread to all people because all sinned ..." (emphasis added).
That strikes me as super important to this discussion, the fact that (a) death spread to all people (b) because all sinned. It doesn't say that death spread to all the world, thus including animals, but rather to all people. And it's because all sinned, which further underscores that it's not talking about animals because they can't sin, nor was Adam their federal head. As we read the entirety of Romans 5:12-21, it is abundantly clear that the object is people, either in Adam or in Christ. I don't see any way to make this passage about animals.
But something equally as important is being omitted in these discussions, namely, what is death? It seems like everyone has assumed this is about biological death, an assumption that everyone is taking for granted and running with, for nobody has bothered to make that case. But shouldn't Romans 5:21 (cf. Gen 2:17) give us a moment of pause? If Paul is talking about death in a biological sense (i.e., physically deceased), how can sin reign therein? It does not make sense to speak of sin reigning in a corpse.
His fall and federal headship caused all men to be sinners.
Exactly, thus "death spread to all people because all sinned." Did death spread to all animals? That's not what it says. If you're going to make that case, you'll have to cite something other than Romans 5, which undermines that idea.
The fall affected all of creation.
Literally nobody is disputing that. In fact, people seem to keep agreeing with it. What is being denied is that Adam's fall resulted in death spreading to all animals, and Romans 5 and 8 do not prove the case you're trying to make.