I almost succeeded in putting latex fonts in R graphics, but it's slightly off

I am studying latex graphics. I have created latex plots with standalone but I am trying to generate R plots with latex fonts. Through online tutorials, here is my dataset code Iris

in RStudio (I modified the example code to make it work. Once I know how to fix the frame, I can study the code in more detail):

library(tikzDevice)
options(tikzMetricPackages = c("\\usepackage[utf8]{inputenc}",
                               "\\usepackage[T1]{fontenc}", "\\usetikzlibrary{calc}",
                               "\\usepackage{amssymb}"))
## I need the amssymb package because I use \mathcal and \mathbb
tikz("formula.tex", width = 4, height = 4, standAlone = TRUE,
     packages = c("\\usepackage{tikz}",
                  "\\usepackage[active,tightpage,psfixbb]{preview}",
                  "\\PreviewEnvironment{pgfpicture}",
                  "\\setlength\\PreviewBorder{0pt}",
                  "\\usepackage{amssymb}"))
par(mar = c(4, 4, 0.1, 0.1), mgp = c(2, 0.9, 0))
library(tikzDevice)
options(tikzMetricPackages = c("\\usepackage[utf8]{inputenc}",
                               "\\usepackage[T1]{fontenc}", "\\usetikzlibrary{calc}",
                               "\\usepackage{amssymb}"))
## I need the amssymb package because I use \mathcal and \mathbb
tikz("formula.tex", width = 4, height = 4, standAlone = TRUE,
     packages = c("\\usepackage{tikz}",
                  "\\usepackage[active,tightpage,psfixbb]{preview}",
                  "\\PreviewEnvironment{pgfpicture}",
                  "\\setlength\\PreviewBorder{0pt}",
                  "\\usepackage{amssymb}"))
par(mar = c(4, 4, 0.1, 0.1), mgp = c(2, 0.9, 0))
plot(iris$Sepal.Length, iris$Sepal.Width, main="Iris sepal length vs width measurements", xlab="Length", ylab="Width")

dev.off()

tools::texi2pdf("formula.tex")
system(paste(getOption("pdfviewer"), "formula.pdf"))

      

        
        
        
      

    

Which gives me:

I would like to have a little more free space on the right, so that 8 comes in completely and fixes the header. The inner image should be smaller and the title lower if possible.