Your examples of science textbooks don't state that Haeckel's hypothesis is true. In fact they don't even state Haeckel's hypothesis which is: that development (ontogeny) repeats the evolutionary history (phylogeny) of the organism - that if we evolved from a fish that evolved into a reptile that evolved into us, our embryos physically echo that history, passing through a fish-like stage and then into a reptile-like stage.

Showing that embryos of different animals look similar in their early stages is not saying that our embryo actually becomes a fish, then a reptile, then a monkey, then a man, which is what Haeckel was hypothesizing.

Your examples still don't quote a biologist as saying that vestigial means useless. In fact, you haven't even provided a biologist quote saying that the tonsils, appendix or any other human organ you mentioned is vestigial. Is there some part of the request that I was unclear on?

I understand that you literally believe that the Genesis creation is true. The question I had was how do you determine if a particular passage is allegory, parable, metaphor, or literal? What are the elements in the writing that tell you, for example, that the prodigal son was a fictional character used for illustration and no a historical person?