Just adapt it with the width you want (the 4 there is the number of characters you want the number to have).
echo "set numberwidth=4" >> ~/.vimrc
Note that you must have the +linebreak compile option on in order for this to work. To check if you have this flag type :echo has('linebreak') in your vim (0 means you don't have it).
tmux has the rectangle-toggle command for this. It's not fully explained in the man page; it only appears in the list of commands available during copy mode:
Command vi emacs
[...]
rectangle-toggle v R
It switches between the line-based selection you demonstrate, and rectangular selection (similar to Vim's blockwise visual mode). In the latter mode, you can start your selection at static and extend down+right without taking in anything to the left (the line numbers).
Best Answer
To enable line numbering:
To disable it: