I think painting the walls lighter and brighter is the right move but don't be restricted to white necessarily - although that would be the safe option and you know for sure it would work! You could introduce a contrasting colour on the ceiling if the walls were white obviously dependent on your furnishings and other colour choices. How about a soft grey or "greige" as an alternative to the white? Finally, you could introduce a dado rail at approx 1m from the floor - painted white the same as cornice and ceiling and then paint the upper and lower sections in contrasting colours of say charcoal on the base and white above or 2 shades of the same colour.

I quite like the red! It's very striking.

Really hard to tell. I like the lightest one but I'm not very adventurous. You may need to choose one and paint a larger area and see what you think.

Have a look at Dulux Flooded Gum. Come back and let us know if you want a darker or lighter suggestion. Dulux actually have a colour called Warn Grey but it is quite browny. You’ll need to try samples in situ because colours on screen are only a guide.