I could search for a custom slider for brow if such thing exist (wich I'm pretty sure it does)
Just saying....but does someone know where to find a shirt that match more the picture ? because he is suppose to have a collar and now he doesn't...

I don't think that the thickness of his brows is so far off that it really warrants throwing a custom slider at it. But, if you really want to go the route of sliders, the brow thickness is one of bella3lek4's sliders. The original thread for that has been locked and the sliders removed. You will have to get them from an alternate download source. I believe Iggysaurus is hosting them here.

I'll download it because it has some that can be usefull like the eye and mouth (specially this one)
but as I said do someone know where I could find the t-shirt with collar (i that what it is call ? I speak french sorry)

No, I don't. You should try looking through this site.

So far I've found this :

and that :

but it can't be merge i guess ?

or I've found this one :

Oh, no, I didn't mean you should get that slider. I just wanted to finetune the brow so it doesn't make that fold over his eye. I know that the brow thickness slider can cause such a fold, so I thought that might be the one. But since you don't use that slider, it's probably the brow height. So just see if that can be tuned, and don't worry about getting more sliders. I really don't think they're necessary.
As for clothes, try the WCIF section: http://www.modthesims.info/forumdisplay.php?f=559