Instead of a literal ^M in the file, just use <CR>. And I think you mean "set hidden". And regarding E173: You can :qa, which won't lose any unsaved changes.

Instead of a literal ^M in the file, just use <CR>. And I think you mean "set hidden". And regarding E173: You can :qa, which won't lose any unsaved changes. And the proper vim package for Debian or Ubuntu is "vim". "vim-full" is the old name and it just installs "vim".