I'm a noob but some other people already answered some of your questions for me so I will try to help.
I want to get muscular but not big, lean and mean, is 5x5 the one for me?
Which exercises can i focus on to work on my abs?
5x5 is good, but you should stick to a good 5x5 program and record your progress always(a notebook and a pen would work great for that).
In order to build some muscles you have to make sure your are progressivelly increasing your work load.
Abs are just another muscle group, you should do some classic ab exercises, but focus on doing something like 12 to 15 repetitions and when that get easy using only your bodyweight use some weight to exercise your abs.
Is my diet in general correct for what i want to achieve?
Should I drop the rice/pasta element of the dinner ( I've been taking quinoa last few weeks but don't wanna eat only that everyday!)
should I be eating 4 meals?
Should I be taking some kind of protein smoothie after working out?
As a rule of thumb people use 1g protein per lbs of body weight ( or something like 2g per kilo ). As long as you are achieving that you should have no problem if you don't want to take a protein smoothie. But it surely gets easier to achieve that mark with one.
4 meals are fine.
You don't have to drop anything of your dinner if your caloric intake is ok for your needs. To figure out the number of calories you need you could search for some formula on google to have a number to start with(all the formulas are just good guesses). Lets say you find out you need 2400 calories for your goal, you should consume around that number of calories and start noticing the changes on your body. If you are gaining too much unwanted weight you should decrease that number, if you are losing too much weight you should increase it.
That's about it =)
Hope I helped, if anyone could improve my answer it would be great.
Good luck and work hard.