Actually, as far as scripture is concerned, there are only two times mentioned with regard to anybody getting together on the first (day) of the week - John 20:19 and Acts 20:7. There is never any mention of them ever again being together on the first.
The John reference has them together in a closed room after the crucifixion because they were afraid of their fellow Jews. Nothing is said about a worship service. And it couldn't have been in recognition of the resurrection because at that time they didn't even believe that the resurrection had taken place.
And the Acts reference might very well have had them getting together to break bread with Paul because he happened to be in town and wanted to talk to them before he had to leave again. The "breaking of bread" can simply be saying that the disciples got together to eat a meal on this one particular first day of the week . The phrase, "to break bread", does not have to refer to a religious service - unless it is specifically stated - but to dividing loaves of bread for a meal. "It means to partake of food and is used of eating as in a meal...... The readers [of the original New Testament letters and manuscripts] could have had no other idea or meaning in their minds" (E.W.Bullinger, Figures of Speech Used in the Bible, pp. 839,840.
But even if the breaking of bread mentioned always did refer to the Lord’s Supper, it had nothing to do with placing a special emphasis on the first (day) because Acts 2:46 says that they broke bread every day. And nothing is said about the resurrection in the account. There simply is no reason for thinking
And as for your analogy of the "Trinity never once directly stated in Scripture as being the Trinity, it is undeniably true through proper handling of the Scripture", the idea that the Lord's Day (the term of which is mentioned only once in scripture) is never even implied in scripture as being referring to the first day of the week.
Actually, no, those two passages are not the only relevant passages.
1 Corinthians 16:2 Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come.
Paul gave an apostolic command to all the Corinthians for an activity that they all were to do specifically on the first day of the week. Such activity plainly gives special emphasis to that day and accords fully with their assembling weekly on that day to worship God corporately.
Furthermore, concerning Acts 20:7, note what the context is:
Acts 20:6 And we sailed away from Philippi after the days of unleavened bread, and came unto them to Troas in five days;
where we abode seven days. 7 And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
Even though they had been there seven days, they did not gather with the disciples to break bread until the first day of the week. Their doing so accords fully with their placing special significance on that day.