Well, I commented on this topic because it looked interesting and already I got rewarded. Thanks for your kind reply. Though long-winded, I thought it was better to mention my various learning opportunities. Yes, I agree, I think Ichihashi Sensei was referring to people thinking Shinto was polytheistic, whereas pantheism brings to mind a whole array of various cultures who saw "the holy" as omnipresent. In some coffee shop conversations after practice, we heard about the concept of "wake-mitama" as if pieces of God were present throughout nature and within each of us.
This is not far from what many Christian clergy are teaching about the presence of God in all of us, or at least the nearness of God, rather than in some remote Heaven among the planets or beyond them.
I don't claim to be able to explain what is to me a vague reassurance of something that is enough for me for now. I go to the services when I can and absorb what I can of Pastor's sermons for the Bible education and the relevance for our world today. I think the message of Jesus for today is vital, whether it is those words or something similar by some pastor, lama, priest or rabbi I think the importance is that as many people as possible learn these things and spread them however they can. The influence of the martial arts is twofold, spreading the message of improvement of society by raising the consciousness of its people to their true nature as connected to each other spiritually and to manifest this feeling in their actions to the best of their ability and understanding. The second is to give an opportunity for people to gather in a training that improves body and spirit, provides a way to defend oneself and others as humanely as possible depending on circumstances and ability, and to hopefully have some conversations about working together to benefit the community nearby or at a distance from them, to borrow from a thread on the possiblity of martial arts influencing the larger society.
With regard to sin, I think that in Japanese it is called "tsumi". and I think the concept of purification was explained in several discussions that the goal is to accomplish one's own mission in life, and to help others, who may have strayed from their own individual missions in life. There is also a concept which was explained something like the phrase "ha wo migaku" polishing or brushing one's teeth. The sword is also polished, the mirror is also polished, all a similar concept. Life can be a polishing process to improve us. These are some concepts that I have heard applied to the martial arts, sorry if my memory of Japanese language isn't very accurate. I remember talking with the former rector of our parish while my parents were still alive, mentioning my various studies, and he too used the word "journey" as a matter of fact that's where I first heard that concept. It's nice that you used the exact same word!
I'm just adding some ideas I heard about in case you find any of them interesting enough to comment and add something similar or even vaguely related from your own study and belief. Of course, any other points you make on other topics will be eagerly read.