Hello Raffaele,
> Apologize if this point has been addressed in previous thread(s) but didn't
> find any archive search engine.
http://www.nabble.com/linux-audio-user-f13236.html
If using a distribution optimised for realtime and audio (like
64studio, Planet CCRMA or Ubuntu Studio) is no option for whatever
reasons, i'm sorry not to be able to help regarding the other
question.