Under
self.contents = Bitmap.new(width - 32, height - 32)
in class Window_Beast in def initialize add this below:
if $fontface != nil
self.contents.font.name = $fontface
self.contents.font.size = $fontsize
elsif $defaultfonttype != nil
self.contents.font.name = $defaultfonttype
self.contents.font.size = $defaultfontsize
end