1. A comma does not "obviously" belong at the end of Col. 1:21, as it reads quite plainly as it is. This verse would be such from prior to the PCE, from at least, if not before, the 1769 Edition, but I haven't checked it out.
2. The "1611" would refer to the readings and translation of 1611, obviously, editions show improvement, such as, correction of typographical errors and editorial standardisation.
3. Yes, I am aware of what the ABS did in the 1850s, you can read all about all such things in my book, "Guide to the PCE" on my website.