You make good points and are very knowledgeable. I’m aware of the two additions you mention.

It’s possible that the changes to which I refer do not create any major theological disharmony regarding fulfilment of the Messiahship. Perhaps in your opinion they may be minor, but to my mind they are significant, at least sometimes. May I refer you to Bart Ehrman’s book Misquoting Jesus, subtitled The Story Behind Who Changed the Bible and Why. He discusses the issues in detail, and says clearly that many of the changes were unintentional, copying errors, attempts to correct perceived mistakes, and so on, therefore innocent, but perhaps sometimes significant.

One important change that he discusses occurs in Luke, which is to do with what is known as Adoptionism. I’ve discussed this in more detail in an earlier article:

Was Jesus Divine, the Son of God? — 1. The Adoptionist Problem | by Graham Pemberton | Medium

Here’s a quote from that:

“Compare the text above “Thou art my Son, the Beloved; with you I am well pleased” with “You are my Son, today I have begotten you”. Ehrman believes that the latter is the earlier, and therefore more authentic, version in that it ‘was quoted a lot by early church fathers in the period before most of our manuscripts were produced. It is quoted in the second and third centuries everywhere from Rome, to Alexandria, to North Africa, to Palestine, to Gaul, to Spain’ (p159). (If it was quoted by them, perhaps this is what they actually believed)”.

I then said that “an early version of Luke, of the Synoptic Gospels the most in line with Christianity as we have come to know it, has an apparently blatant adoptionist statement, which has been changed by later editors to conform to the Christian message. Ehrman argues that Luke may not have intended this. I am not so sure”.

Perhaps you don’t agree, but this change makes an important theological difference, since it suggests that Jesus was not born God incarnate, as implied elsewhere in Luke, and stated openly in John, but became specially favoured in some way at the time of his baptism. That is definitely different from the Christian theology we are now invited to believe.