> Do normal Christians not have an agenda?
Not normal Christians, no. Just truth-seekers like many other people. But once you have found the information that fits the criteria of truth, you settle into an equilibrium of confidence.
> Are they incapable of lying?
Christians are capable of lying, just like anyone else. We're taught that it is wrong, but some Christians do it anyway.
> Are they incapable of making mistakes about the text?
Christians are capable of making mistakes about the text. That's why we work so hard to study it well and correctly, as objectively as possible, using all the information at our disposal. It's a scholarly discipline, but it's also common sense, and we have to be careful not to look at or interpret the text with colored lenses of bias or distortion.
> Is there a way to verify interpretations like running experiments to refine a hypothesis?
History and literature are not like a science lab. We can run experiments on anything to do with Alexander the Great or Julius Caesar. These events are forever gone; they cannot be viewed directly or reconstructed precisely or exhaustively. They cannot be subjected to scientific observation and experimentation. Our knowledge of the past, as in history, comes to us exclusively through incomplete, selective, and even biased sources (like the inscriptions on the tombs of Egyptian kings). It's not possible to "run experiments." Science does science, and not every field is subject to "science."
There are ways to verify interpretations, though the discipline of literary biblical interpretation is complex. It involves paleo-linguistics, study of ancient culture, anthropology, sociology, archaeology, historical studies of artifacts and documents, theology, and literature. By assessing all the data in the templates of the varied disciplines, there are ways to arrive at bona fide interpretations about which we can be confident to a high degree.
> Do you think faith is a valid method to claim that other religions are true? Your examples all deal with physical evidence- grocery stores exist and so do cars.
Christianity also deals with physical evidence. The existence of David, Hezekiah, Isaiah, Jesus, and Paul. The truth of the Babylonian destruction of Jerusalem, the Israelite return from the exile, and the physical and cultural evidences of Jesus's resurrection. The Bible is evidentiary, and doesn't call for blind faith.
Science itself uses not just empirical evidence, but also theoretical or conceptual reasoning (formulating and articulating questions, developing and clarifying hypotheses, models, and theories) and also analysis (data processing, weighing data, calculating parameters for error, data reduction, data analysis, and data interpretation). It's not all about the physical evidence, ever. Everything needs to be interpreted.
> So are unfalsifiable religious supernatural ideas true by default through faith?
Nothing is true by default. Everything has to go through a grid of criteria for truth.
I read an interesting article a few month ago that had been published just a few years back (
https://www.pbs.org/wgbh/nova/article/falsifiability/) about how nonfalsifiability enters even the scientific realm. Falsifiability, it turns out, is not a perfect criterion. But we certainly respect science nonetheless.
> So my question is how would you apply Occam’s Razor to the claims made by Christians when we take into account the fact that we think all other religions are invented by man?
Christianity has a sufficiency of explanation that other religions don't have. There are really only two religions in the world: Judeo-Christianity and Hinduism. Islam is at root a cult (distortion) of Christianity, as are Jehovah's Witnesses and Mormonism. Buddhism is a subset of Hinduism, having taken god(s) out of the picture. Confucianism is a philosophy, not a religion. We're left with Christianity and Hinduism.
Yet there are many aspects of Hinduism that don't square with reality: Life is an illusion, suffering is an illusion, truth is relative (and not necessarily true), nature (and therefore humanity) is impersonal, etc. We can all see the inconsistencies putting Hinduism against reality. Hinduism is also a philosophical religion, not a historical one. Not an ounce of it is provable.
Christianity, however, fulfills the criterion of truth and has sufficiency of explanation (where even science lacks it). There is a natural connection between theism and causality: intelligence, personality, intent, freedom, power, and laws. Theism has sufficient prior probability (simplicity of explanation) and complete explanatory power. The intrinsic probability of theism is, relative to other hypotheses about what there is, very high. Therefore, theism fulfills the obligations of Occam's Razor as being the simplest and most straight-forward explanation.