R code and Sweave output - EDIT

UPDATED Question 1 In the lattest update of KnitR the output is clean as what I expected. Maybe an update was made.

The new output :

Before update

I’m trying to get a particular output with Sweave and R code.
For now I have this code :

documentclass[11pt,french]{report}
  usepackage{babel} %%french
  usepackage{amsmath,amsfonts,amssymb} %%maths
  usepackage[utf8]{inputenc}   % LaTeX
  usepackage[T1]{fontenc}      % LaTeX
  usepackage[dvipsnames,table,xcdraw]{xcolor}
  %% Background code chunk
  usepackage{listings}
  usepackage{color}

  definecolor{codegreen}{rgb}{0,0.6,0}
  definecolor{codegray}{rgb}{0.5,0.5,0.5}
  definecolor{codepurple}{rgb}{0.58,0,0.82}
  definecolor{backcolour}{rgb}{0.95,0.95,0.92}
 %% background code chunk listing
  lstset{
    language=R}
lstdefinestyle{mystyle}{
    backgroundcolor=color{backcolour},   
    commentstyle=color{codegreen},
    keywordstyle=color{magenta},
    numberstyle=tinycolor{codegray},
    stringstyle=color{codepurple},
    basicstyle=footnotesize,
    breakatwhitespace=false,         
    breaklines=true,                 
    captionpos=b,                    
    keepspaces=true,                 
    numbers=left,                    
    numbersep=5pt,                  
    showspaces=false,                
    showstringspaces=false,
    showtabs=false,                  
    tabsize=2
}

lstset{style=mystyle}

witch is coming from this site.

The R code I’m trying to implement is :

%% script R
begin{lstlisting}[linerange=begin{Sinput}-end{Sinput},includerangemarker=false, caption = Code source en R pour l'exemple]
<<eval =FALSE>>=
# dataset
x <- c(2,3,6,9,12); y <- c(2,5,3,6,5)

# Estimations des parametres
reg <- lm(y ~ x)

# Resume de l'estimation
summary(reg)

# Valeurs de Yt
fitted(reg)

# Residus 
residuals(reg)
@
end{lstlisting}

The output :

My questions :

1- How can I get a better output for the ~ symbol ?

2- Is there a way to eval the code without getting and output like this ?

<<eval = TRUE, echo=FALSE, fig=TRUE, height=4,width=4.5>>=
[...] precedent code
@