I didn’t read most of what you posted (although I will), but for example Ephesians 4:30 - being sealed unto the day of redemption (KJV) is somewhat different than being sealed for the day of redemption.
The former give assurance that the seal will be there all the way until the day of redemption, and the latter can be construed as the believer is sealed in Christ, but does not seem to indicate assurance that seal is there for good. Some might say that I’m splitting hairs with this, but I don’t think so.
Just a quick glance at a search turns up this: av1611.com/kjbp/articles/flanders-whykjv.html (Why We Use the King James Version of the Bible). If you can please at least read the highlights.
At any rate, I am NOT looking to argue or appear more knowledgeable or experienced than you. I am made of the same flesh and blood and subject to the same imperfections as anyone.
Just trying to participate in what is arguably one of the most important discussions any of us could ever have.
εἰς eis, ice; a primary preposition; to or into (indicating the point reached or entered), of place, time, or (figuratively) purpose (result, etc.); also in adverbial phrases:—(abundant-)ly, against, among, as, at, (back-)ward, before, by, concerning, + continual, + far more exceeding, for (intent, purpose), fore, + forth, in (among, at, unto, -so much that, -to), to the intent that, + of one mind, + never, of, (up-)on, + perish, + set at one again, (so) that, therefore(-unto), throughout, til, to (be, the end, -ward), (here-)until(-to), …ward, (where-)fore, with.
Also, from the same source: The KJV translates Strong's G1519 in the following manner: into (573x), to (281x), unto (207x), for (140x), in (138x), on (58x), toward (29x), against (26x), miscellaneous (322x).