I love your careful thought process here and the layouts with the inspo pics are beautiful -- I think you've really captured the textures and tones and effects you are going for and these combinations look very much like "you" to me! Love the Fair Isle with the fun socks and the subtle pattern mixes.
Brooklyn is an incredible muse! I keep saying I want to make a study of her posts and do something similar.
On the subject of cold spring, this is something that I, too, am just learning to dress for. We had cold spring in Ontario, too, but the cold was of an entirely different order. There's no such thing as warm spring there. It's straight from cold cold spring to summer. So it didn't really make sense to develop outfits for cold spring -- it was more a case of buying some winter items in spring colours.
Here, I feel differently. I will say, as a small warning -- I won't wear my wide cropped jeans until warm (er) spring here. Too cold. Mind you, I don't wear socks that show with my crops -- will only wear no show socks, and my footwear these days is all sneakers all the time (except for my indoor clogs). All this to warn that crops that are wide might feel too "airy" for cold spring, depending on your other layers. I will wear slim or tapered crops but not wide ones in those temps. And to encourage you to seek tapered or cuffed options for cold spring.
Like you, I've never been a chinos fan. Have never found a pair I feel good in. But I can imagine a more tapered style working.
I also hear you 100% on skirts/ dresses. I don't wear them regularly (except for special occasions/ going out -- what's that? hahah) until warm spring / early summer.