A Kind is a Species. The terms are synonymous but the classification system accepted today doesn't offer a clear definition so I don't attempt to define it beyond something like Cats, Dogs, Bears and Giraffes.
That sounds too much like a small child just learning to talk for whom everything with four legs is either a "doggie" or a "horsie".
That also violates the original reason for the "originally created kinds" argument, which was to make room inside the Ark for all these multitudes of species that the goat-herders sitting around the campfires repeating these stories could never have imagined. Not to mention the impossible task for Noah to travel all over the globe into every single ecological niche to collect all of them, not to mention the even more impossible task of delivering each and every one to them back to where they would need to go. So the solution was that those hundreds and even thousands of different species we find all originated from a very few "originally created kinds" which then hyper-evolved almost instantaneously to all the species we know.
Plus, you completely kill the basic "microevolution" argument that you want to promote. If a kind is a species, then every single species of cat is a separate kind, which you say cannot intermingle. You have just killed your position.
I often use Kind instead of Species because Species is a term the ToE defines in ways that don't apply to what I think a Kind is.
Uh, no. Not in the least. The classification system was developed by Carl Linnaeus in the mid-1700's, at least a full century if not more before Darwin published. He came up with species, so it is most definitely not a ToE term.
Now, the problem we face is the species problem, just how to we recognize that we are looking at a different species. Reproductive barriers is one way, but there are at least two flavors of that: 1) genetic inability to reproduce, and 2) they just never meet or there is no "urge to merge". And those two basic barriers can also be subdivided further (eg, differing degrees by ability to create hybrids, is the separation purely geographical or are they just mutually repugnant).
There should never have been a problem recognizing that a Species varies within itself so I don't know why there ever was a problem or why it ever changed if it did.
Within a species, no. But between two species which are still interfertile, yeah there can be a problem if the sexual signals don't work. Dr. Jonathan Miller, MD (PBS' "The Body in Question" some decades ago) wrote a wonderful primer which I think was Darwin for Beginners (various editions available on amazon.com), in cartoon format. In that, he described the situation where the phenotypes are too different so that then "the f**k is off".
There can also be a problem where the genetics are a bit too off. Some hybrids are fertile and some are not. How can "variation within a single species" account for that? Variation within a single species should always produce fertile offspring. So why would that sometimes fail? Your "variation within a single kind" cannot explain it, yet evolution can.