Hi Chiara,
I'm a petite pear with short legs, so I "get" many of your issues, even though you are much taller than I (Knightly also has short legs, which is almost impossible to tell, given her thin frame and styling aplomb). Losing the waistline is life-changing for shapes like ours, since we relied on showing off that narrow point to keep our silhouettes flattering. I actually started reading 40-50+ fashion bloggers to see what silhouettes flattered mature bodies.
The AHA moment for me was learning to dress for my vertical body, rather than just my horizontal body. Like you, I already knew that anything that bulked up my shoulders--wide necklines, jackets, scarves, necklaces and earrings--was my friend. But what I hadn't mastered was the trick of lengthening the leg line as far as possible (since the bottom half of my body is shorter and wider than the top half), which for me meant starting at my natural waist and continuing through my toes. Now, I look for wide, flared, and trouser leg pants (fitted through hip and thigh, since those are my widest points) with vertical creases paired with heels, pencil skirts, and straight maxis, so that I don't add bell-shaped width to an already larger and shorter bottom half.
I think you've hit on this concept by noticing that your tops must stop right at the start of your hip bone. This allows for tops to cover your new waistline without infringing detrimentally on the leg line. I'm finding that the new cropped tops (including sweaters) work wonders in this regard. They are boxy, which gives our waists room to breathe, while they also stop soon enough. If there is a gap between your top and your bottom piece, you can experiment with camis underneath that match your bottom piece, thus tricking the eye to extend that leg line without calling attention to your middle. As you mentioned, slouchy tees also work if you use the half-tuck in the center. I would think high-low tops also do the trick. All of this illustrates Angie's "just flattering enough" concept. Her seafoam spring post (with different bottoms for me) are a good visual:
http://youlookfab.com/2015/03/.....or-spring/
...and the BR cropped top she recommends is my new go-to (it's fabulous; I bought the petite):
http://bananarepublic.gap.com/.....aff2379092
Color is important for me, too. My bottoms are always darker than my tops...although this spring and summer, I will be experimenting with focusing on "I" on top with lighter bottoms, by which I mean wide, stripes, and brights on top to draw attention away from lighter (but still leg-lengthening) bottoms.
The low-rise skinny bottom with non-matchy-matchy-untucked-top years almost killed my fashion sense. Those trends are my worst fashion-don'ts, and so I'm glad that fashion disaster decade (for me) is over!
Good luck to you!