That is an interpretation in such places as Acts 20:7, and i read two sides, and am not convinced of your take on it, while it is far more important how you see sabbath and feast keeping and dietary laws being a necessary part of salvific faith obedience.
Nothing abouth the sabbath has anything to do with “dietary laws.” This is a new smoke screen that you are errecting to dodge the solid facts.
Each of the “first day” meetings that you have listed is a part of a feast. First Fruits, and Pentecost account for all of the meetings that you can come up with.