I love this post. My journey was identical. For anyone experiencing this steep learning curve here is my advice. It’s a case of laying out your grids and sections and clearly labeling everything in your layer tree. Don’t bother doing what we’ve all done, by trying to untangle the ball of wool.
It will go on for ever! instead create a blank site and in desktop mode alt and tab between your broken design and you fresh new copy. Use what you have learnt to lay out your grid and sections and simply copy and paste the content between the 2 sites. Put the content in the correct grid locations and repeat. As you populate each section, work down your break points one at a time from Desktop down. Doing it this way allows you to really get the structure right as you go. Trust me it will be a lot easier this way. Editor X is actually incredible, you