These are all very interesting points, as this is my favourite film of all time and I have seen it 20+ times, but never really made anything of that line. I have the 'still screwing?' subtitle version and can't speak French, but I feel people are reading far too much into it.
It appears to me that Said knows Asterix is crazy, but is a necessary evil. He has to keep him happy long enough to get his money, so small talk bordering on flattery is what he decides on. He's clearly not 'above' Asterix in the banlieu's social hierachy so he has no option to scare him into paying up and instead has to play along with his stupid behaviour. On the flip side, Asterix knows Said is 'below' him in intimidation/respect standing, and is looking for an excuse to not give him the money. Vinz provides the excuse, and although I hate the character of Asterix, I have to give him his due!
King of Wipe Castle: What the? You're not made of Tuesday!
it appears asterix was high on coke and whatnot. the word screwing he uses also refers to what he was doing with those three brickheads - he was screwing with them and wanted them to get out of his place as quickly as possible to never return. he reminds me of a character from boogie nights - the rich weirdo the di(kheads tried to rob.
my vote history: