Playing A LOT of rounds of CS:GO Madre realise that my reaction times and anticipation skills, well, stink. What can I do to improve it, aside from more practice and low settings?

Headphones can be your friend. They can allow you to hear them from certain sides.
Sensitivity can also help you. If your turning too slow with your mouse, raise it little by little until it's at a good rate for you personally so you can easily turn corners without flailing your mouse around.
Static items can also throw you off. Best advice I can offer on that one is just be cautious on every sight, the slightest movement can be another person.

You shouldn't beat yourself up too much. When I started playing CS:S, it was very difficult to take down anyone. Other than practicing, the only thing you can do to help yourself is learn patterns that people tend to take on maps. Once you start to realize what people are likely to do, you can prepare yourself. The same goes with just about any FPS really.