But he doesn’t identify it as the first day of the week. Since it has been mentioned that John’s vision is about the events of the end times (Isaiah 2:6-22) it makes more sense that that is what the phrase is referring to.
 
No, it really doesn't. While John's visions are ABOUT the end times, yes, what is said in Rev. 1:10 is that John was in the Spirit ON the Lord's Day. Unless you would like to claim that everything mentioned in that passage of Isaiah was actually happening around John as he had his vsion, you're really stretching that application.
 
Yes, this is the meaning post scriptural men decided to attribute to the phase in order to give support for their desire to change observance from the seventh day to the first day.
I'm curious, why do you suppose they'd want to change it?
 
As mentioned above, yor appeal to "the day of the LORD" as being the same as "the Lord's Day" in Rev. 1 has obvious problems.  
Saying so doesn’t make it so. Your reference didn’t document a first century usage of the phrase: "3 days and 3 nights" to mean anything other than at least parts of 3 days and at least parts of 3 nights.
 
You say this while completely ignoring all the proof texts the citation mentioned, lol. Unless you believe the Bible contradicts itself (do you?) then "three days and three nights" has to mean the same thing as "on the third day" and "after three days" and "in three days," which are also descriptions of when Christ rose.  
Again, no documentation has been shown that supports this idea.
When you don't actually interact with the argument being made, I can see why the case would be so cut and dry for you. *shrug* 
 
 
re: " We see this, e.g., in 1 Sam 30:12-13..."
I see nothing here that precludes at least parts of 3 nighttimes and at least parts of 3 daytimes.
 
The beginning of the chapter indicates that the events happened on "the third day" since David had begun his trek back to the land of the Philistines. So his eating there, after victory, doesn't necessitate a third night to have transpired, for example. Two nights had gone by, and these things happened, "on the third DAY."
The irony is that even you, here, and making the phrase non-literal, by inserting "part of" in front of days and nights. Yet there's no reason to do so. I suppose I'm going to have to dig up some Biblical scholars for you on this.  
 
re: "That would be an odd way of phrasing it in this context. Friday is the first day, Saturday is the second day, Sunday is the third day."
But that is the way that you phrased it in your post #13: "Sunday is the third day from Friday."
Yes, but I didn't say the "first day from" whenever, because the "from" is unnecessary. The first day is the first day. Again, this isn't that complicated.
If Sunday is the third day from a certain day, then Saturday is the second day from a certain day, and Friday is the first day from a certain day, which makes Thursday the certain day.
Again, this is simply inaccurate. Jesus was crucified on Preparation Day, which is by definition, Friday:
"Now when evening had come, because it was
the Preparation Day, that is, the day before the Sabbath," Mark 15:42 
 
If you’re referring to your comment tacked on to the end of your Acts 15 discussion, I’m afraid I don’t see where Paul says what you seem to be suggesting
One person esteems
one day above another; another esteems every day
alike. Let each be fully convinced in his own mind. He who observes the day, observes
it to the Lord; and he who does not observe the day, to the Lord he does not observe
it. Romans 14:5-6, cf. Colossians 2:16-17
 
I do not currently have one.
 
OK, so do you believe in God? Do you believe Jesus is the Son of God? Do you believe the Bible is inspired Scripture? How about the Trinity? Generally atheists wouldn't be that interested in this topic.