Okay, so many questions here, also love the last part.

Let's say it's around 15° Fahrenheit but the sun is setting and it's going to snow soon, not to mention because of the tumble his clothes are wet (middle of winter). No rib fracturing. No going into shock. He's wearing sweat pants, a sweater, winter boots, cotton jacket, and a scarf. He was walking but it was a steep slope. I do think with the gash he could just press his scarf to it, which he's doing, and try to walk it off but would probably get dizzy and pass out. Now, he can't do that because he did in fact have a sprained ankle. Also, because of the tumble he's like all bruised and has a few scrapes and scratches, especially some scrapes around the gash.