Despite your derisive tone, yes, science does have presuppositions, e.g. the uniformity of natural law; and biases, e.g. a bias against ad hoc explanations.
The distinction between "natural" and "supernatural" therefore is hardly arbitrary if, by a "supernatural" agent, we mean (as most English speakers do) one that can supersede natural law at will or whim.
Now, science is simply a means of trying to understand the natural world. Its methods, presuppositions and biases have been determined by what experience and results teach about what works best in advancing this aim.
If you can demonstrate how a science without the presupposition of uniform natural law can actually work in advancing usable or perspicuous knowledge of the natural world, go ahead. Or encourage others more able to do so. Scientists will gladly, as they have at various times previously, abandon or modify their operational presuppositions in order to admit a genuinely useful theory or principle.
WARNING/HINT: "Genuinely useful" is the tricky part.
You wrote: "Ask science again "what is 'natural?'" and all it can say is "whatever can be known by science or is not "supernatural." Talk about low standards for precision. Talk about circular reasoning. Most of all talk about presuppositions and biases. And this from a pursuit that is by its very nature dedicated to true knowledge."
Reply:
I am curious about what you mean by "true knowledege". If one observes that X-rays behave in such and such fashion, as observed by scientists (physicists, chemists, radiologists), where is the place for "an intelligent deisgner"? X-rays are not mentioned even once in the Bible. They seem to be naturalistic in origin. Do you have an objection to how X-rays behave?
Could you say where the understanding of X-rays is "circular reasoning"?