One could make his choice using the "eeny, meeny, miney, moe" technique, but it wouldn't be an intelligent choice. From a creationist viewpoint, because all creatures were created at once, one could select anything at all. I don't know about you, but I wouldn't be too happy about taking a new "toad-tested" medicine, even if the creationist researcher assured me that all creatures are equally unrelated to us, so a toad is as good a test subject as an ape.
To make a truly intelligent choice, one would need to find a very closely related test subject. But once we talk about "closely related" we're in dangerous territory, aren't we? Be glad the researchers are evolutionists. You may one day have your life saved by the products of their research.
No. Not at all. I don't understand why you see it that way. Relationships between living creatures are how the world was established. It is quite natural to seek them, observe them, and make use of them.