It's the "usual" dark brown for a reason The mahogany works best with richer colors. You pretty much can't go wrong with the dark brown. It definitely isn't as sophisticated or eye-catching, but it 's very versatile.
I doubt it will have any shine. I have a few silk cotton blend pieces of clothing and they have a more cashmere-like feel. On a side note, if you're looking at it shouldn't you able to see if it shines?
I wear my suede shoes all the time in the snow and have never had an issue with them becoming spotty. Just be careful around salt. That will destroy your suede and unlike leather, it won't be reversible.
It most definitely can reamin unbuttoned. It's really just preference. The whole point of not leaving your jacket open is so that you aren't exposed. That isn't an issue with a 3pc. I personally leave it unbuttoned.
I've got two suits with tears on them. I went to the local weaving place but after seeing their work would prefer to ship it out to a reputable place. Does anyone have experience with a company that accepts mail-ins?
Being as I have a larger than average head, I don't look good with unstructured jackets. I tried building up the shoulders on one of my unstructured jackets, and while it looks okay, to the discerning eye, it is visible. If you won't wear it otherwise, it's worth a shot. Just make sure to find a decent tailor.